Therapeutic alliance (TA), or the collaborative relationship between a therapist and client, has been shown to be an important component of intervention success. The objective of this study was to examine the psychometric properties of the Therapy Process Observational Coding System-Alliance Scale (TPOCS-A). The sample consisted of 20 children (19 males) ages 8 to 12 years with autism and their parents (15 mothers, 5 fathers), who completed a cognitive-behavioural intervention designed to improve children's emotion regulation skills. Two trained coders rated early, middle, and late parent and child alliance using the TPOCS-A after watching video recorded therapy sessions. Therapist-reported child involvement, alliance, and adherence were also assessed. Psychometric findings revealed that the TPOCS-A is a reliable and valid measure of therapeutic alliance for children with autism. The implications of examining TA in empirically supported treatments for this population are discussed.