Although widely conceived as distinct conditions, higher-functioning autism spectrum disorder (ASD) and schizoid personality disorder (schizoid PD) share similar clinical symptomatology. This study explored the relationship between the two disorders by collecting extensively validated measures of autistic trait burden (Social Responsive Scale, Second Edition) and schizoid PD affectation (Diagnostic Interview for Genetic Studies) from clinically ascertained verbal males with and without autism ages 12 to 25 years (N = 72) via parent, teacher, and self-report. Although only a small minority of adolescents with ASD met full diagnostic criteria for schizoid PD, participants with ASD endorsed a continuous distribution of schizoid PD traits that reflected a pronounced pathological shift in comparison with those in the control group, with one half of ASD males experiencing three or moreDiagnostic and Statistical Manual of Mental Disorders, 4th Edition schizoid PD criterion items “often” or “almost always.” Results suggest significant amplification of schizoid PD trait burden in adolescents with ASD. ASD-specific interventions should be considered for patients with schizoid PD with premorbid histories of ASD.