Evidence suggests young people with autism spectrum disorder (ASD) have lower levels of emotion regulation than typically developing peers and struggle to modulate the frequency and intensity of their emotions. It may be that these emotion regulation difficulties are a result of co-occurring alexithymia rather than being a core symptom of ASD. We explored the associations between alexithymia and emotion regulation in 43 young people with ASD, aged 10 - 18 years, through self and parent report questionnaires. Parents completed questionnaires measuring the young person's emotion regulation skills and ASD symptom severity. The young people completed measures of emotion regulation and alexithymia. Correlational analysis and linear regression were used to investigate the relationships between ASD severity, alexithymia and emotion regulation. As predicted, high levels of alexithymia and high level of emotion dysregulation were reported by the young people. Parents also scored the young people as being high on emotion dysregulation. We found statistically significant correlations between alexithymia and emotion regulation, as reported by young people themselves, with some large effect sizes. Parental report of emotion regulation did not correlate with the measure of alexithymia. The source of discrepancies between parent and adolescent perceptions of emotion regulation and emotion recognition are discussed. These results highlighted the key role emotion regulation difficulties play in the lives of young people with ASD and the association with alexithymia. High levels of alexithymia are likely to impinge on the selection of appropriate emotion regulation strategies. The clinical implications for treatment are discussed.