Social media-based interactions between consumers and firms have received considerable attention in recent years. Despite significant interest in this phenomenon, little is known about how ethnicity impacts consumers' comment intention on social media. This is an important limitation, as ethnicity represents a significant driver of consumer behavior. Addressing this gap, we investigate whether minority (vs. majority) group consumers are more likely to publicly comment on a firm's social media post, when the majority of existing comments is made by ethnically similar consumers. We also explore whether perceived similarity affects these behaviors, and establish the moderating role of ethnic identity, social media usage intensity, and shared content ethnic association (vs. disassociation) in the proposed relationships.To explore these issues, we conduct two survey experiments. The findings reveal ethnicity as an important driver of consumers' intent to comment on firm-based social media posts. Specifically, compared to ethnic majority (i.e., Caucasian) consumers, ethnic minority (i.e., African American) consumers are more likely to comment on a social media post when most of the post's existing comments are made by ethnically similar consumers, owing to their perceived similarity to existing commenters. Moreover, consumers' ethnic identity, social media usage intensity level, and shared content associations play an important role in these relationships.