Exhibit (j)

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Post-Effective Amendment No. 126 to Registration Statement No. 2-14213 on Form N-1A of our reports dated December 20, 2010, relating to the financial statements and financial highlights of Balanced Fund, Capital Value Fund, Focused Growth Fund, Fundamental Equity Fund, Giftrust Fund, Growth Fund, Heritage Fund, New Opportunities Fund, NT Growth Fund, NT Vista Fund, Select Fund, Small Cap Growth Fund, Ultra Fund, Veedot Fund, and Vista Fund, each a series of American Century Mutual Funds, Inc., appearing in the Annual Report on Form N-CSR of American Century Mutual Funds, Inc. for the year ended October 31, 2010, and to the references to us under the headings “Financial Highlights” in each Prospectus and “Independent Registered Public Accounting Firm” and “Financial Statements” in the Statement of Additional Information, which are part of such Registration Statement.

/s/ DELOITTE & TOUCHE LLP

DELOITTE & TOUCHE LLP

Kansas City, Missouri

February 24, 2011