Although most research conceptualizes emotion regulation as an internal process (i.e., intrapersonal), emotions are frequently regulated in an interpersonal context. Adolescents may be particularly prone to turn to peers for assistance, given that honing emotion regulation abilities is a key task and peers become increasingly important at this stage. Adolescents each participated with a self-nominated same-gender friend (total N = 186; M age = 15.68 years). All participants provided self-reports of their own emotion regulation difficulties and their engagement in interpersonal behaviors (excessive reassurance seeking, negative feedback seeking, conversational self-focus, self-disclosure) as well as their perceptions of their friends’ engagement in excessive reassurance seeking and conversational self-focus. Using a cross-lagged panel model design, the current study tested associations between adolescents’ intrapersonal emotion regulation difficulties and engagement in self- and friend-reported interpersonal emotion regulation behaviors at 3 time points over 6 months. Gender and age group differences were considered. Results evidenced concurrent and longitudinal associations between emotion regulation difficulties and self-reported maladaptive (excessive reassurance seeking, conversational self-focus, negative feedback seeking), but not adaptive (self-disclosure), interpersonal regulatory behaviors. Friends’ reports of adolescents’ excessive reassurance seeking and conversational self-focus were associated concurrently, but not longitudinally, with self-reported emotion regulation difficulties. Implications for clinical intervention with adolescents struggling to regulate emotions are discussed.