We study the role of regional cultural differences in M&A transactions in the U.S. A larger social trust distance between two companies reduces the likelihood of them combining via an M&A transaction and results in lower completion rates and longer completion times, indicating higher complexity in deal execution. However, a larger social trust distance is also associated with higher gains from mergers, as measured by acquirer and combined announcement returns and medium-term buy-and-hold abnormal returns. This suggests that for these announced deals, the synergy potential is high enough to offset the costs induced by the large cultural distance.