Emotional reactivity (e.g. explosive outbursts, tantrums) is a common but understudied challenge for individuals with autism spectrum disorder. Prior research has relied primarily on questionnaire data or observations of very young children. The current study coded emotional reactivity and recovery during a series of standardized frustration tasks in a sample of psychiatrically hospitalized youth with autism spectrum disorder (N = 150; mean age: 12.76) inclusive of the full spectrum of intellectual and functional abilities and explored relationships between emotional reactivity and participant characteristics. The amount, intensity, and duration of negative affect and total range of affect significantly increased from a baseline period to frustration tasks and significantly decreased during recovery. Younger children displayed more negative affect overall; however, age did not moderate change in affect from baseline to frustration tasks or recovery. Adaptive functioning and verbal ability both moderated change in affect, with individuals with lower adaptive functioning and minimally verbal individuals displaying greater reactivity and less recovery. Reactivity was unrelated to non-verbal IQ, overall autism symptom severity, and parent-reported psychiatric/behavioral problems. The results highlight the feasibility and importance of examining emotional reactivity in more severely affected individuals and suggest the need to develop more targeted interventions for emotional reactivity in this group.