Research has established a positive relationship between the impostor phenomenon and poor mental health outcomes among Black graduate students. However, the literature is scarce on psychosocial factors that could moderate this relationship. The present study investigated Black graduate students’ ( N = 200) experiences of impostorism and whether perceived social support moderated the relationship between impostor phenomenon and symptoms of depression or anxiety. The findings suggested perceived social support moderated the relationship between impostor feelings and both anxiety and depression. The findings suggested that, for the imposter phenomenon-anxiety relation, family social support weakened the association. For the imposter phenomenon-depression relation, total social support, family social support, and significant other social support weakened the association. These findings have important implications for both educational and clinical practice. For graduate programs, they must be aware of the effects imposter syndrome has on Black students and offer supportive environments to these students. For mental health professionals, the findings of this study should inform their work with Black graduate students, specifically intervention decisions to strengthen social support and sense of community.