Autism spectrum disorder (ASD) is characterised by persistent deficits in social communication and interaction as well as restricted, repetitive patterns of behaviour and interests. Early detection and early intervention programmes improve functional outcomes. Family physicians should screen for ASD opportunistically when children attend clinics for acute issues and during scheduled well-child assessments. Early warning signs of ASD include the lack of social gestures at 12 months, using no meaningful single words at 18 months, and having no interest in other children or no spontaneous two-word phrases at 24 months. Children with suspected ASD should be referred to appropriate specialist centres as early as possible for multidisciplinary assessment and diagnosis.