<p>This study compared self- and parent-reported symptoms of oppositional defiant disorder (ODD) in autistic adolescents (<i>n</i> = 34), adolescents who have a history of autism spectrum disorder (ASD) but no longer display symptoms (“loss of autism diagnosis,” LAD; <i>n</i> = 29), and neurotypical (NT; <i>n</i> = 35) adolescents. Participants and their parents completed questionnaires measuring ODD symptomology as part of a larger research study. All participants had age-appropriate cognitive and language abilities, with no group differences. The LAD group had significantly fewer <i>self</i>-reported ODD symptoms compared to both the autism and NT groups, and had significantly fewer <i>parent</i>-reported ODD symptoms compared to the autism group; the LAD and NT groups did not differ. There was a significant negative correlation between self-reported ODD symptoms and age for the NT group; this relationship was not observed in the autism and LAD groups. Findings indicate that LAD adolescents and young adults differed from their autistic and NT peers in their perceptions of their own externalizing oppositional behavior, reporting fewer ODD behaviors. LAD parents also reported fewer ODD behaviors, with strong agreement between parent- and self-report. Symptoms of oppositional behavior should be explored in a longitudinal sample, but results suggest individuals who have lost the autism diagnosis show significantly less ODD externalizing behaviors.</p>