Background <p>Emotion regulation (ER) difficulties are common in autistic individuals and may contribute to co-occurring psychopathology during adolescence. However, age-group heterogeneity in existing research limits understanding of ER processes in autistic adolescents. Therefore, this mixed methods systematic review synthesizes current knowledge on ER in autistic adolescents aged 10–24&#xa0;years.</p> Methods <p>We systematically searched MEDLINE, PsycINFO, Web of Science, and Scopus for empirical studies on ER in autistic adolescents. 32 studies (including two qualitative) met inclusion criteria and were synthesized using a convergent integrated approach.</p> Results <p>Autistic adolescents consistently exhibited more ER difficulties than non-autistic peers, which were associated with internalizing and externalizing symptoms. Greater autism symptom severity, lower theory of mind, and social challenges were frequently linked to lower ER, while no consistent associations with age, gender, or IQ were found. Few studies examined physiological or neurobiological factors, but evidence suggested associations between ER difficulties, lower heart rate variability, and atypical neural responses. Cognitive-behavioral and mindfulness-based interventions generally led to improvements in ER, though results varied and discrepancies between self- and proxy-reports were common.</p> Conclusion <p>ER challenges are pronounced in autistic adolescents and are closely associated with mental health symptoms. While interventions show promise, future research should address measurement heterogeneity, examine neurobiological underpinnings, and include more longitudinal and ecologically valid designs.</p> Trial registration <p>CRD42024529184 (registered April 06, 2024).</p>