Prior studies suggest that firms headquartered in areas with strong religious social norms have higher ethical standards. In this study, we examine whether the ethical standards associated with local religious norms influence the M&A announcement returns. We document that the M&A announcement returns of acquirer firms increase with the strength of religious social norms in the area surrounding firms’ headquarters. We also document that the relationship is attenuated when acquirer firms have strong corporate social responsibility credentials, is amplified when public (...) trust that firms act in the best interest of stakeholders suffers a negative shock and when the M&A deal has greater economic significance for the acquirer, and manifests predominantly in the lower tail of the distribution of M&A returns. Our findings are consistent with investor assessments of firms’ ethical standards driving the relationship between local religious social norms and M&A announcement returns. We find no evidence for the competing explanation—that investor assessments of firms’ risk preferences drive the documented relationship. (shrink)