Adolescence is a period of biopsychosocial change, where some youth thrive while others develop stress-related difficulties, making it crucial to understand the processes that may contribute to poor mental health. This study examined adolescents’ emotion regulation (ER) repertoires and their associations with indicators of mental health, using data pooled across three waves of ecological momentary assessment (EMA), each spaced six months apart. The final sample included 292 adolescents (Mage = 12.55 years, SDage = 0.46; 41.48