Sleep is a modifiable risk factor for suicidal thoughts and behaviors in adolescents, and social media use may be one factor linked to sleep outcomes. The current study examined self-reported subjective daytime and nighttime social media use (SMU) as a predictor of both subjective and objectively- captured sleep (timing, duration, and quality) among adolescents at high risk for suicide in an intensive outpatient program (IOP) for depression and suicidality. Data from two studies were used to evaluate these relationships for one month; Study 1 as part of standard clinical care among adolescents (N = 95, 75% female) and Study 2 as part of an intensive monitoring study among adolescents and young adults in the IOP (N = 30, 67% female). Multilevel modeling indicated that adolescents with more nighttime subjective SMU experienced later self-reported sleep timing and daily SMU predicted poorer sleep quality (Study 1). Both daytime and nighttime subjective SMU predicted later sleep timing as assessed by actigraphy (Study 2). Subjective SMU did not predict sleep duration or quality in Study 2. Findings suggest that SMU may be one actionable factor to improve sleep timing, which has implications for suicide prevention among individuals at high risk for suicide.