Exhibit 23

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in the Registration Statement on Form S-8 (Nos. 333-41458, 333-78417, 333-30375, 333-126734) of ADTRAN, Inc. of our report dated March 2, 2006 relating to the financial statements, management’s assessment of the effectiveness of internal control over financial reporting and the effectiveness of internal control over financial reporting, which appears in the Annual Report to Shareholders, which is incorporated in this Annual Report on Form 10-K. We also consent to the incorporation by reference of our report dated March 2, 2006 relating to the financial statement schedule and the reference to us under the heading “Selected Financial Data”, which appear in this Form 10-K.

/s/    PricewaterhouseCoopers LLP

PricewaterhouseCoopers LLP

Birmingham, Alabama

March 2, 2006