Gay and bisexual men are at increased risk for mood and anxiety (internalizing) disorders relative to heterosexual men. Rejection sensitivity (RS), or the anxious expectation of rejection, is associated with depression and social anxiety symptoms among lesbians and gay men as well as generalized anxiety symptoms among sexual minority women. However, it remains unclear if it is associated with other internalizing symptoms, such as panic and posttraumatic stress symptoms. Further, research on the comorbidity of mental disorders suggests that a latent transdiagnostic internalizing factor (INT) accounts for the co-occurrences between mood and anxiety disorders. Although previous research has found that the associations between discrimination and mental disorders can be explained by INT, research has yet to examine if this extends to the associations between RS and internalizing symptoms. Using a sample of young gay and bisexual men (N = 101), we examined the associations between RS and internalizing symptoms (depression, social anxiety, generalized anxiety, panic, and posttraumatic stress). Additionally, we examined the extent to which these associations were mediated by INT. Results indicated that RS was significantly associated with social anxiety, generalized anxiety, and posttraumatic stress symptoms, and that INT fully mediated these associations. As such, findings support RS as a transdiagnostic risk factor for internalizing symptoms among gay and bisexual men.