We study the effect of corporate cultural similarity on merger decisions and outcomes. Using the similarity in firms’ corporate social responsibility characteristics to proxy for cultural similarity, we find that culturally similar firms are more likely to merge. Moreover, these mergers are associated with greater synergies, superior long-run operating performance, and fewer write-offs of goodwill. Our evidence is consistent with the notion that cultural similarity eases post-deal integration. Our results contribute to the literature on the determinants of merger success, provide new evidence on the impact of corporate culture, and offer a new approach to defining firms’ cultural similarity.