<p>Diversity is a hotly debated topic in public discourse, which motivates scholars to investigate how group diversity impacts observers’ judgments of the group. Recent findings have suggested a positive link between group diversity and perceived morality of the group because people perceive diverse (vs. non-diverse) groups to be more capable of perspective-taking. However, studies testing this theory have been predominantly conducted in the WEIRD (Western, Educated, Industrialized, Rich, and Democratic) societies. In this conceptual replication and extension, we tested whether the “diversity → perceived perspective-taking → perceived morality” link could be generalized across societies differing in cultural tightness-looseness (i.e., whether a culture prescribes tight or loose adherence to collective norms). Across five replication studies (<i>N</i> = 3659), we found that while the positive impacts of group diversity on perceived perspective-taking and morality replicated among loose cultures, no credible evidence supported the effects for participants in tight cultures, or those who perceived their culture as tight. By directly manipulating cultural tightness-looseness, we obtained causal evidence that tight (vs. loose) cultural contexts elevate perceived perspective-taking and, subsequently, perceived morality of non-diverse groups, thereby attenuating differences in perceived morality between diverse and non-diverse groups. The results call for more attention to the views of diversity across different cultures.</p>