Previous research suggests that social anxiety disorder (SAD) has a specific relationship with impairment in friendship quality; however, potential moderators of this relationship have not been tested. The current study examines whether the specific effect of SAD on friendship quality is stable or varies across gender and ethnicity in a large epidemiological dataset. Results indicate that the underlying construct of friendship quality differed slightly but significantly between men and women; as a result, effects of SAD were tested in men and women separately. After partially constraining friendship quality across ethnic groups, our results indicated that the relationship between SAD and friendship quality remained robust in all groups. In addition to replicating the finding that SAD specifically relates to perceived friendship quality, the current study highlights the need to test whether underlying constructs such as friendship quality are consistent across the groups that make up heterogeneous samples.