Alexithymia is a personality trait frequently found in adults with autism spectrum disorder (ASD), and has been linked to impairments in emotion recognition and empathy. The presentation of alexithymia within ASD at younger ages remains unexplored, and was examined in the present study. Alexithymia rates were significantly elevated in ASD (55%; 31/56 scoring above cut-off) versus non-ASD adolescents (16%; 5/32 scoring above cut-off). Within individuals with ASD, alexithymia was associated with increased self-reported anxiety, parent-reported emotional difficulties, self-reported sensory processing atypicalities, and poorer emotion recognition, but was not associated with theory of mind ability. Overall, our results suggest that alexithymia is highly prevalent, and has selective cognitive correlates in young people with ASD.