Using a sample of 664 merger and acquisition (M&A) transactions and office‐level audit data, this study investigates the role of auditors in M&A completion time. We find that having a common auditor for both acquirer and target firms in M&A transactions increases the completion time of such transactions because the exposure to higher litigation and reputational costs outweighs the information‐access advantage of common auditors. However, auditors' past experience in M&A transactions helps reduce completion time and costs. These results are robust to having Big N auditors at both ends as well as to various acquirer, target, and deal characteristics.