Objective: The purpose of this study was to evaluate aspects of emotion dysregulation (ED) that characterize young adolescents with ADHD, examine the effects of subtype and comorbidity, and determine the extent to which ED is related to aggression and rule-breaking and social impairment. Method: We examined which aspects of ED are most relevant to ADHD in 180 young adolescents (75% boys), as well as whether ED differs across ADHD subtypes or comorbid oppositional defiant disorder (ODD) status. We also examined the association between ED and aggression, rule-breaking, and social impairment. Results: Young adolescent females and males with ADHD exhibited various manifestations of ED, including behavioral dyscontrol in the presence of strong emotions and inflexibility/slow return to emotional baseline. ED did not differ as a function of ADHD subtype or comorbid ODD. Three aspects of ED, namely, low threshold for emotional excitability/impatience, behavioral dyscontrol in the face of strong emotions, and inflexibility/slow return to baseline, predicted three of six measured indices of parent- and self-reported social impairment, above and beyond comorbid ODD. Conclusions: ED is associated with ADHD among young adolescents, does not differ based on ADHD subtype or ODD status, and is associated with social impairment.