BACKGROUND The formation of romantic relationships and friendships in adolescence is a defining milestone in the progression toward social maturity. Thus, examining adolescents' friendship and romantic experiences serves a vital role in understanding their psychological adjustment. OBJECTIVE The main purposes of the current study were to examine (a) whether romantic involvement, romantic security, and friendship closeness were independently predictive of late adolescents' depression and loneliness, and (b) whether friendship closeness would moderate the negative effects of adolescents' lower degrees of romantic involvement and romantic security on depression and loneliness. METHODS Data came from 12th grade adolescents (N = 110, 53 females) as well as their parents and a same-sex best friend. Adolescents reported on their romantic involvement, romantic security, and psychological distress. Parent reports of adolescents' depressive symptoms and friend reports of friendship closeness were also included. RESULTS Higher degrees of romantic involvement and friendship closeness were related to lower degrees of loneliness. Higher degrees of romantic security were related to lower degrees of depression and loneliness. The effect of romantic involvement on depression and loneliness was moderated by friendship closeness. Also, the effect of romantic security on loneliness was moderated by friendship closeness. CONCLUSIONS Future research should focus on the interactive roles that friendships and romantic relationships play in the emergence of psychopathology during adolescence.