Objectives/Background: Despite findings that insomnia and depression have a bidirectional relationship, the exact psychological mechanisms that link these disorders are largely unknown. The goal of this study was to identify whether social support mediates the relationship between insomnia and depression. Methods: The study sample (N = 115) consisted of females only, and all participants (mean age 21.77 ± 1.80) completed self-report measures of insomnia severity, depression, and social support. Results: Insomnia severity was significantly associated with low levels of social support (B = -1.04, SE = .27, p < .001) and high levels of depression (B = .18, SE = 0.05, p < .001). Social support mediated the effects of insomnia on depression (95% CI [.03, .15]). However, social support did not mediate the effects of depression on insomnia (95% CI [-.01, .32]). Conclusions: These findings suggest that interpersonal factors such as social support may be an important factor to consider in female insomnia patients in the context of preventing depression in this population.