Given the recent findings regarding the association between alexithymia and Autism Spectrum Disorder (ASD) and the accumulating evidence for the presence of the Broader Autism Phenotype (BAP) in relatives of individuals with ASD, we further explored the construct of alexithymia in parents of children with ASD as a potential part of the BAP. We hypothesized that (a) parents of children with ASD will demonstrate higher impairment in their emotion processing when compared to controls, and (b) high impairment in emotion processing in parents will be associated with severity of symptoms in children with ASD. Psychometric and diagnostic data were collected on 188 children with a diagnosis of ASD. The Toronto Alexithymia Scale (TAS-20) was completed by 439 parents of children with ASD and a control group of 45 parents of children with Prader Willi syndrome (PW). Results show that ASD parents score higher than controls on the TAS-20 total score. Within the ASD group, children of fathers with high alexithymia score higher on repetitive behaviour symptoms compared to children of fathers with low alexithymia. The alexithymia trait appears to be one of the many building blocks that make up the BAP.