Earnings Release | December 31, 2019

ABOUT GWB Company Snapshot EPS Performance CAGR EPS 10% 3 • Full-service regional bank focused on relationship-based $2.90 $2.92 business and agribusiness banking $2.46 • 175 banking branches across nine states: Arizona, Colorado, $2.31 $2.67 Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota $2.45 $1.90 and South Dakota $2.14 $0.79 $0.77 • Headquartered in Sioux Falls, South Dakota • 5th largest farm lender bank in the U.S. as of 09/30/19 1 FY15 FY16 FY17 FY18 FY19 FYTD 19 FYTD 20 EPS - diluted Adj. EPS - diluted ² Strong Earnings and Efficiency Tangible Book Value 5 per Share Accretion $172 $167 160.00 GWB CAGR TBV 11% 3 $145 150.00 $131 $158 140.00 $109 $121 130.00 $46 $43 120.00 110.00 48% 50% 47% 47% 46% Peer CAGR TBV 7% 3 46% 46% 100.00 90.00 FY15 FY16 FY17 FY18 FY19 FYTD 19 FYTD 20 4QFY141QFY152QFY153QFY154QFY151QFY162QFY163QFY164QFY161QFY172QFY173QFY174QFY171QFY182QFY183QFY184QFY181QFY192QFY193QFY194QFY19 4 Net Income Adj. Net Income ² Efficiency GWB GWB Peer Group Ratio 5 1 3 2 Source: American Banker's Association 4 Compound Annual Growth Rate over 5 years Excludes after-tax effect of items with a significant impact to net income that we do not believe to 5 See appendix for Peer Group listing; data sourced from SNL Financial be recurring in nature, such as one-time acquisition expenses or the effect of revaluation of Non-GAAP measures, see appendix for reconciliations 2 deferred taxes

EXECUTING ON STRATEGY • Total loans decreased 0.8% to $9.63 billion during the quarter Focused Business • Loan decline was mainly attributable to the commercial non-real estate segment of the portfolio, which Banking Franchise decreased by $43.5 million, or 2.5% and a reduction in the agriculture segment of $28.0 million, or 1.4% with Agribusiness • Deposits decreased by 2.1% to $10.09 billion during the quarter, driven by a reduction in the use of brokered Experience deposits offset by increases in both consumer and business deposits • Fully diluted EPS 1 of $0.77 for the quarter compared to $0.89 for 4QFY19 Strong Profitability • Profitability remains strong with ROTCE 1 of 15.0% and ROAA of 1.34% for the quarter Driven by a Highly Efficient Operating • Efficiency ratio 1 of 46.2% for the quarter compared to 44.5% for the prior quarter Model • All regulatory capital ratios remain above minimums to be considered “well capitalized” Strong Capital • Quarterly dividend of $0.30 per share Generation and ◦ Dividend payable February 26, 2020 to stockholders of record as of the close of business on Attractive Dividend February 12, 2020 • Net charge-offs of $6.1 million during the quarter represent 0.25% of average total loans on an annualized basis, majority of which were in agriculture and commercial non-real estate segments of the loan portfolio Focus on Credit • Loans graded "Substandard" increased by 35.5% to $640.1 million during the quarter and loans graded and Key Asset "Watch" increased by 2.6% to $416.3 million primarily due to downgrades in the agriculture and agriculture- Quality Metrics related segment, with a small number of downgrades in the commercial non-real estate segment • Nonaccrual loans increased by 45.6% to $156.1 million during the quarter primarily due to a small number of agriculture loans identified as we continue to work through the higher risk credits 1 This is a non-GAAP measure. See appendix for reconciliation. 3

REVENUE Revenue Highlights Net Interest Income ($MM) and NIM • Net interest income (FTE) decreased 1.4% to $106.7 million compared to prior quarter $108.2 $106.7 $106.4 $106.7 ◦ Interest income included a $2.0 million net reversal of interest income on loans moved to nonaccrual during the quarter 3.70% 3.68% 3.81% 3.68% • NIM (FTE) adjusted NIM (FTE) 2 was down 2 and 4 basis points, respectively, compared to 4QFY19 3.69% 3.65% 3.81% 3.65% • Noninterest income increased $0.6 million compared to prior quarter due to wealth management fees increasing as a result of the purchase and assumption of management of trust assets 4QFY19 1QFY20 FYTD 19 FYTD 20 in Colorado Net Interest Income (FTE) NIM (FTE) Adjusted NIM (FTE) ² NIM Analysis Noninterest Income 1 Service charges Other Service fees 0.01% $1,481 3.70% 0.02% 3.68% $2,569 0.14% 0.03% 3.69% 3.65% Wealth management (0.14)% $2,964 (0.07)% (0.03)% OD/NSF fees $3,986 Mortgage banking income, net $1,612 Loans Other 4QFY19 Deposits 1QFY20 Derivatives Borrowings $1,165 Brokered CDs Interchange income $3,373 Cash & Investments Nonaccrual Interest 1 Chart excludes changes related to loans and derivatives at fair value which netted $(1.4) million NIM (FTE) Adjusted NIM (FTE) ² for the quarter and gain/loss on sale of securities. Dollars in thousands. 2 Adjusted NIM (FTE) is a non-GAAP measure. See appendix for reconciliations. 4

EARNINGS, EXPENSES & PROVISION Highlights Net Income ($MM) • Net income of $43.3 million, a decrease of 13.9% over 4QFY19 $50.3 $45.8 $44.5 • Higher provision for loan losses during the quarter due $43.3 mainly to an increase in specific reserves in the agriculture, CRE and commercial non-real estate $26.8 segments • ROAA of 1.34% and 15.0% ROTCE 1 for the quarter 1.55% 1.48% 1.44% 1.34% • Efficiency ratio 1 was 46.2% for the quarter 0.84% • Noninterest expense remained stable from 4QFY19 1QFY19 2QFY19 3QFY19 4QFY19 1QFY20 Net Income Adjusted Net Income ROAA Noninterest Expense ($MM) Provision for Loan Losses ($MM) Sustained peer-leading $8.1 $8.1 efficiency ratio 1, 2 $55.2 $56.9 $57.1 $56.9 $5.2 46.1% 46.2% 44.5% 46.2% $2.0 4QFY19 1QFY20 FYTD 19 FYTD 20 4QFY19 1QFY20 FYTD 19 FYTD 20 Noninterest expense Efficiency Ratio 1 ROTCE and efficiency ratio are non-GAAP measures. See appendix for reconciliations. 5 2 See appendix for Peer Group listing; data sourced from SNL Financial.

BALANCE SHEET OVERVIEW Balance Sheet Highlights Total Loans ($MM) • Outstanding loans decreased $80.5 million, or 0.8%, during the $9,416 $9,707 $9,626 quarter $8,683 $8,969 ▪ Decline in the quarter due to the commercial non-real $7,325 $864 estate segment, which decreased due to disbursement $7,819 transaction timing within our mortgage warehouse lending, the agriculture segment, which was impacted by the workout of a small number of large credits and the CRE segment, which had a small number of loans refinance with other institutions at lower rates • Deposits declined $211.8 million, or 2.1%, during the quarter FY15 FY16 FY17 FY18 FY19 1QFY20 ▪ Decrease during the quarter was driven by a decrease in brokered deposits offset by increases in both consumer Total Loans Loans Acquired and business deposits Deposits ($MM) Capital 13.0% 13.0% $10,300 12.7% $9,733 $10,089 12.5% 12.1% 12.2% $8,605 $8,978 $7,387 12.0% 12.0% $863 1.05% 11.7% $7,742 11.4% 0.86% 10.9% 11.1% 0.65% 9.7% 0.40% 9.6% 9.6% 0.32% 0.32% 9.2% 8.3% 8.5% FY15 FY16 FY17 FY18 FY19 1QFY20 FY15 FY16 FY17 FY18 FY19 1QFY20 Total Deposits Deposits Acquired Cost of Deposits Tier 1 Capital Total Capital TCE / TA ¹ 1 TCE / TA is a non-GAAP measure. See appendix for reconciliation. 6

ASSET QUALITY Highlights • Asset quality remains a key focus as we make progress working through substandard credits and higher risk credits in both ag and non-ag portfolios • Watch remained relatively stable for the quarter • "Substandard" loans increased $167.6 million, or 35.5%, primarily due to downgrades in the agriculture and agriculture-related commercial non-real estate segments • Later in the year we will transition to a rating system that better aligns with industry standards and offers better granularity, particularly the adoption of a Special Mention category within a Criticized Loan classification Watch Loans ($MM) Substandard Loans ($MM) $640 $406 $416 $216 $206 $197 $343 $328 $310 $312 $84 $472 $123 $121 $132 $115 6.6% $253 4.2% 4.2% 4.3% $242 $233 4.9% 3.8% 3.6% $81 3.5% $184 $111 $71 2.8% 2.5% 2.6% 2.7% $130 $189 $205 $180 $259 $200 $219 $54 $131 $162 $172 $357 $424 FY15 FY16 FY17 FY18 FY19 1QFY20 FY15 FY16 FY17 FY18 FY19 1QFY20 Ag Loans Non Ag Loans % of Total Loans Ag Loans Non Ag Loans % Total Loans 7

ASSET QUALITY Highlights Nonaccruals / Total Loans 83.8% • Nonaccrual loans increased 45.6% for the quarter due to a small number of agriculture loans identified as we continue 66.0% to work through the higher risk credits. 51.1% 46.6% • Net charge-offs for the quarter were 0.25% of average 45.9% 45.1% 0.29% loans on an annualized basis, down from 0.31% of 0.67% 0.42% 0.38% average total loans on an annualized basis for the prior 0.30% quarter 0.60% 1.12% 1.14% 1.33% 0.79% 0.80% • The ratio of ALLL to total loans increased to 0.76% for the 0.33% quarter from 0.73% as of the prior quarter FY15 FY16 FY17 FY18 FY19 1QFY20 AG Non-AG Reserves/ Total NALs Net Charge-offs / Average Total Loans 2 Comprehensive Credit-Related Coverage ($MM) 0.36% GWB Legacy Loans Amortized Acquired 0.02% Cost Fair Value Loans Total 0.26% 0.08% 0.25% ALLL $ 70.2 $ — $ 2.6 $ 72.8 0.02% Remaining Loan Discount $ — $ — $ 11.9 $ 11.9 0.18% 0.06% Fair Value Adjustment (Credit) $ — $ 6.2 $ — $ 6.2 0.13% 0.14% Total ALLL / Discount / FV Adj. $ 70.2 $ 6.2 $ 14.5 $ 90.9 0.12% 0.03% 0.25% Total Loans $ 8,441.3 $ 772.2 $ 412.7 $ 9,626.2 0.02% 0.10% 0.18% ALLL / Total Loans 0.83 % — % 0.63 % 0.76 % 0.11% 0.05% 0.08% Discount / Total Loans — % — % 2.88 % 0.12 % 0.04% 0.02% 0.04% FV Adj. / Total Loans — % 0.80 % — % 0.06 % FY15 FY16 FY17 FY18 FY19 FYTD 20 Total Coverage / Total Loans ¹ 0.83 % 0.80 % 3.51 % 0.94 % CRE AG C&I Other Total Loans 1 Comprehensive Credit-Related Coverage is a non-GAAP measure that Management believes is useful to demonstrate that the FV adjustments related to credit and remaining loan discounts consider credit risk and should be considered as part of total coverage 2 8 Annualized for partial periods

AG LOAN ASSET QUALITY Commentary Ag Net Charge-offs / Average Total Loans 1 • Charge-offs continue to be driven by loans in the cattle sector while substandard and watch levels for beef are 0.01% showing improvement • Upgrades in dairy loans were more than offset by downgrades to substandard as a lag in customer financials has resulted in a deterioration of rating metrics and stalled 0.19% potential portfolio improvements • Two loans in the swine sector were downgraded as 0.03% 0.18% performance and metrics have been pressured by weak 0.05% prices in the latter part of the year, primarily from tariffs 0.02% 0.07% 0.05% 0.03% 0.03% FY15 FY16 FY17 FY18 FY19 FYTD 20 Ag Watch Loans by Category 2 Ag Substandard Loans by Category 2 $16 $48 $25 $24 $76 $16 $9 $19 $12 $44 $35 $40 $90 $195 $230 $63 $123 $13 $67 $103 $14 $21 $15 $28 $145 $69 $22 $69 $86 $96 $30 $75 $73 $64 $75 $31 $94 $79 $62 $35 $23 $51 $47 FY15 FY16 FY17 FY18 FY19 FYTD 20 FY15 FY16 FY17 FY18 FY19 FYTD 20 Grains Beef Cattle Dairy Farms Hogs All Other 1 Annualized for partial year periods 2 Categories with less than $20m were considered immaterial and combined in Other 9

PROVEN BUSINESS STRATEGY Focused Business Banking Franchise with Agribusiness Experience Attract and Retain High-Quality Relationship Bankers Invest in Organic Growth While Optimizing Footprint Deepen Customer Relationships Explore Accretive Strategic Acquisition Opportunities Strong Profitability Driven by a Highly Efficient Operating Mode Strong Capital Generation and Attractive Dividend Focus on Credit and Key Asset Quality Metrics 10

DISCLOSURES Forward-Looking Statements: This presentation contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Statements about Great Western Bancorp, Inc.’s expectations, beliefs, plans, strategies, predictions, forecasts, objectives, assumptions or future events or performance are not historical facts and may be forward-looking. These statements are often, but not always, made through the use of words or phrases such as “anticipates,” “believes,” “can,” “could,” “may,” “predicts,” “potential,” “should,” “will,” “estimate,” “plans,” “projects,” “continuing,” “ongoing,” “expects,” “views,” “intends” and similar words or phrases. In particular, the statements included in this Presentation concerning Great Western Bancorp, Inc.’s expected performance and strategy, the outlook for its agricultural lending segment, strategies for managing troubled loans, and the interest rate environment are not historical facts and are forward-looking. Accordingly, the forward-looking statements in this Presentation are only predictions and involve estimates, known and unknown risks, assumptions and uncertainties, that could cause actual results to differ materially from those expressed. All forward-looking statements are necessarily only estimates of future results, and there can be no assurance that actual results will not differ materially from expectations, and, therefore, you are cautioned not to place undue reliance on such statements. Any forward- looking statements are qualified in their entirety by reference to the factors discussed in the sections titled “Item 1A. Risk Factors” and "Cautionary Note Regarding Forward-Looking Statements" in Great Western Bancorp, Inc.’s Annual Report on Form 10-K for the most recently ended fiscal year, and in other periodic filings with the Securities and Exchange Commission. Further, any forward-looking statement speaks only as of the date on which it is made, and Great Western Bancorp, Inc. undertakes no obligation to update any forward-looking statement to reflect events or circumstances after the date on which the statement is made or to reflect the occurrence of unanticipated events. Non-GAAP Financial Measures: This presentation contains non-GAAP measures which our management relies on in making financial and operational decisions about our business and which exclude certain items that we do not consider reflective of our business performance. We believe that the presentation of these measures provides investors with greater transparency and supplemental data relating to our financial condition and results of operations. These non-GAAP measures should be considered in context with our GAAP results. A reconciliation of these non-GAAP measures appears in our earnings release dated January 28, 2020 and in Appendix 1 to this presentation. Our earnings release and this presentation are available in the Investor Relations section of our website at www.greatwesternbank.com. Our earnings release and this presentation are also available as part of our Current Report on Form 8-K filed with the Securities and Exchange Commission on January 28, 2020. Explanatory Note: In this presentation, all financial information presented refers to the financial results of Great Western Bancorp, Inc. combined with those of its predecessor, Great Western Bancorporation, Inc. 11

Appendix 1 Non-GAAP Measures

NON-GAAP MEASURES At or for the three months ended: December 31, September 30, June 30, March 31, December 31, 2019 2019 2019 2019 2018 Tangible net income and return on average tangible common equity: Net income - GAAP $ 43,274 $ 50,285 $ 26,783 $ 44,511 $ 45,786 Add: Amortization of intangible assets, net of tax 377 315 335 343 344 Tangible net income $ 43,651 $ 50,600 $ 27,118 $ 44,854 $ 46,130 Average common equity $ 1,908,519 $ 1,885,785 $ 1,864,132 $ 1,822,940 $ 1,817,052 Less: Average goodwill and other intangible assets 748,146 745,349 745,718 746,107 746,503 Average tangible common equity $ 1,160,373 $ 1,140,436 $ 1,118,414 $ 1,076,833 $ 1,070,549 Return on average common equity * 9.0 % 10.6 % 5.8 % 9.9 % 10.0 % Return on average tangible common equity ** 15.0 % 17.6 % 9.7 % 16.9 % 17.1 % * Calculated as net income - GAAP divided by average common equity. Annualized for partial-year periods. ** Calculated as tangible net income divided by average tangible common equity. Annualized for partial-year periods. Adjusted net interest income and adjusted net interest margin (fully-tax equivalent basis): Net interest income - GAAP $ 105,173 $ 106,709 $ 105,629 $ 103,475 $ 104,894 Add: Tax equivalent adjustment 1,523 1,487 1,424 1,442 1,490 Net interest income (FTE) 106,696 108,196 107,053 104,917 106,384 Add: Current realized derivative gain (loss) (890) (127) 321 405 21 Adjusted net interest income (FTE) $ 105,806 $ 108,069 $ 107,374 $ 105,322 $ 106,405 Average interest-earning assets $ 11,543,610 $ 11,609,823 $ 11,617,521 $ 11,345,559 $ 11,086,800 Net interest margin (FTE) * 3.68 % 3.70 % 3.70 % 3.75 % 3.81 % Adjusted net interest margin (FTE) ** 3.65 % 3.69 % 3.71 % 3.76 % 3.81 % * Calculated as net interest income (FTE) divided by average interest earning assets. Annualized for partial-year periods. ** Calculated as adjusted net interest income (FTE) divided by average interest earning assets. Annualized for partial-year periods. 13

NON-GAAP MEASURES At or for the three months ended: December 31, September 30, June 30, March 31, December 31, 2019 2019 2019 2019 2018 Adjusted interest income and adjusted yield (fully-tax equivalent basis), on non-ASC 310-30 loans: Interest income - GAAP $ 117,709 $ 124,923 $ 124,098 $ 121,528 $ 120,361 Add: Tax equivalent adjustment 1,523 1,487 1,424 1,442 1,490 Interest income (FTE) 119,232 126,410 125,522 122,970 121,851 Add: Current realized derivative gain (loss) (890) (127) 321 405 21 Adjusted interest income (FTE) $ 118,342 $ 126,283 $ 125,843 $ 123,375 $ 121,872 Average non-ASC 310-30 loans $ 9,554,161 $ 9,693,395 $ 9,699,433 $ 9,615,096 $ 9,435,901 Yield (FTE) * 4.96 % 5.17 % 5.19 % 5.19 % 5.12 % Adjusted yield (FTE) ** 4.93 % 5.17 % 5.20 % 5.20 % 5.12 % * Calculated as interest income (FTE) divided by average loans. Annualized for partial-year periods. ** Calculated as adjusted interest income (FTE) divided by average loans. Annualized for partial-year periods. Efficiency ratio: Total revenue - GAAP $ 120,906 $ 121,732 $ 116,395 $ 121,698 $ 121,614 Add: Tax equivalent adjustment 1,523 1,487 1,424 1,442 1,490 Total revenue (FTE) $ 122,429 $ 123,219 $ 117,819 $ 123,140 $ 123,104 Noninterest expense $ 56,930 $ 55,212 $ 56,000 $ 56,580 $ 57,106 Less: Amortization of intangible assets 427 366 385 394 394 Tangible noninterest expense $ 56,503 $ 54,846 $ 55,615 $ 56,186 $ 56,712 Efficiency ratio * 46.2 % 44.5 % 47.2 % 45.6 % 46.1 % * Calculated as the ratio of tangible noninterest expense to total revenue (FTE). 14

NON-GAAP MEASURES At or for the three months ended: December 31, September 30, June 30, March 31, December 31, 2019 2019 2019 2019 2018 Tangible common equity and tangible common equity to tangible assets: Total stockholders' equity $ 1,920,669 $ 1,900,249 $ 1,881,128 $ 1,852,394 $ 1,812,008 Less: Goodwill and other intangible assets 749,481 745,197 745,563 745,947 746,341 Tangible common equity $ 1,171,188 $ 1,155,052 $ 1,135,565 $ 1,106,447 $ 1,065,667 Total assets $ 12,845,520 $ 12,788,301 $ 12,954,896 $ 12,830,162 $ 12,573,641 Less: Goodwill and other intangible assets 749,481 745,197 745,563 745,947 746,341 Tangible assets $ 12,096,039 $ 12,043,104 $ 12,209,333 $ 12,084,215 $ 11,827,300 Tangible common equity to tangible assets 9.7 % 9.6 % 9.3 % 9.2 % 9.0 % Tangible book value per share: Total stockholders' equity $ 1,920,669 $ 1,900,249 $ 1,881,128 $ 1,852,394 $ 1,812,008 Less: Goodwill and other intangible assets 749,481 745,197 745,563 745,947 746,341 Tangible common equity $ 1,171,188 $ 1,155,052 $ 1,135,565 $ 1,106,447 $ 1,065,667 Common shares outstanding 56,382,915 56,283,659 56,939,032 56,938,435 56,938,435 Book value per share - GAAP $ 34.06 $ 33.76 $ 33.04 $ 32.53 $ 31.82 Tangible book value per share $ 20.77 $ 20.52 $ 19.94 $ 19.43 $ 18.72 15

Appendix 2 Accounting for Loans at FV and Related Derivatives

LOANS AT FAIR VALUE & RELATED DERIVATIVES Overview • For certain loans with an original term greater than 5 years with a fixed rate to the customer, Great Western Bank (“GWB”) has entered into equal and offsetting fixed-to-floating interest rate swaps with two US counterparties • Total size of the portfolio was $772.2 million at December 31, 2019 GWB has elected the Fair Value Option (ASC 825) on these loans and applies a similar treatment to the related derivatives: ◦ Changes in the fair value of the loans and the derivatives and the current period realized cost (benefit) of the derivatives (i.e., the net pay fixed/receive floating settlement) are recorded in earnings through noninterest income ◦ This differs significantly from most peers who have elected Hedge Accounting treatment ◦ The historical election is irrevocable so the concept will be present for the foreseeable future in GWB’s financial statements even if different accounting elections are made on future originations ◦ Management presents non-GAAP measures to provide more clarity on the underlying economics Summary x Income Statement Line Item: x x Net (decrease) increase in fair value of Net realized and unrealized gain (loss) x loans at fair value on derivatives Net Relationship Notes (Decrease) increase in FV related to interest rates $ (12,799) $ 12,799 $ — 1 (Decrease) increase in FV related to credit $ (2,134) $ 389 $ (1,745) 2 Increase in SWAP fees $ — $ 1,218 $ 1,218 3 Current period realized cost of derivatives $ — $ (890) $ (890) 4 Subtotal, loans at FV and related derivatives $ (14,933) $ 13,516 $ (1,417) 5 1 Equal and offsetting each period. Changes in the FV of each financial asset and liability driven by current compared to contractual rates. 2 Management records an adjustment for credit risk in noninterest income based on loss history for similar loans, adjusted for an assessment of existing market conditions for each loan segment. The FV adjustment related to credit is not included in the ALLL but loans are included in the ALLL coverage ratio denominator. 3 Swap fees are fees related to transacting interest rate swaps and other interest rate derivatives. 4 Current period actual cost of fixed-to-float interest rate swaps. Within non-GAAP financial measures, management reclassifies this component to interest income, resulting in adjusted interest income, adjusted net interest income and adjusted NIM, reflecting the underlying economics of the transactions. All else equal, this drag on earnings will reduce as short-term LIBOR rates increase. 5 While US GAAP mandates the presentation of these items in noninterest income, management believes the residual net amount economically represents the net credit exposure of this segment of the portfolio - presented as a "credit-related charge" in the earnings release and elsewhere (see note (2)) - and the current period derivative cost which should be analyzed relative to gross interest income received from the loan customers (see note (4)) as presented in non-GAAP measures. 17