Background: Understanding adaptive behaviour variability in children with autism spectrum disorder (ASD) may have important implications for early intervention. The purpose of this study was to explore whether autism symptom severity and caregiver depression affected adaptive behaviour in young children with ASD. Method: Data were collected from 60 primary caregivers of children aged 2-6 years with ASD. A factorial multivariate analysis of covariance was conducted to investigate if different levels of autism symptom severity and caregiver depression affected communication, socialisation, and daily living skills, after controlling for child age. Results: Findings suggest that only autism symptom severity accounted for significant variance in adaptive behaviour, with socialisation being most impacted. Although more than half of the caregivers reported heightened depressive symptoms, caregiver depression was not related to adaptive behaviour. Conclusions: Findings highlight the level of functional impairment that young children with ASD experience in relation to autism symptom severity.