Introduction: Severe mood dysregulation and problems (SMP) in otherwise typically developing youth are recognized as an important mental health problem with a distinct set of clinical features, family history and neurocognitive characteristics. SMP in people with autism spectrum disorders (ASDs) have not previously been explored. Method: We studied a longitudinal, population-based cohort of adolescents with ASD in which we collected parent-reported symptoms of SMP that included rage, low and labile mood and depressive thoughts. Ninety-one adolescents with ASD provided data at age 16 years, of whom 79 had additional data from age 12. We studied whether SMP have similar correlates to those seen in typically developing youth. Results: Severe mood problems were associated with current (parent-rated) and earlier (parent- and teacher-rated) emotional problems. The number of prior psychiatric diagnoses increased the risk of subsequent SMP. Intellectual ability and adaptive functioning did not predict to SMP. Maternal mental health problems rated at 12 and 16 years were associated with SMP. Autism severity as rated by parents was associated with SMP, but the relationship did not hold for clinician ratings of autistic symptoms or diagnosis. SMP were associated with difficulty in identifying the facial expression of surprise, but not with performance recognizing other emotions. Relationships between SMP and tests of executive function (card sort and trail making) were not significant after controlling for IQ. Conclusions: This is the first study of the behavioural and cognitive correlates of severe mood problems in ASD. As in typically developing youth, SMP in adolescents with ASD are related to other affective symptoms and maternal mental health problems. Previously reported links to deficits in emotion recognition and cognitive flexibility were not found in the current sample. Further research is warranted using categorical and validated measures of SMP. (Contains 5 tables.)