["Journal of Intellectual Disability Research, EarlyView. ", "\nABSTRACT\n\nBackground\nAutism spectrum disorder (ASD) is common in individuals with Down syndrome (DS), with an estimated prevalence of 16%–18%. However, receiving a dual diagnosis of Down syndrome and ASD (DS + ASD) is often delayed. Little evidence exists on the path to ASD diagnosis nor interventions to support individuals with DS + ASD. Barriers to diagnosis and treatment for this unique patient population have yet to be described. This study explores clinicians' practices and perceptions regarding the diagnosis and treatment DS + ASD, and the barriers their patients face in connecting to recommended evaluations and services.\n\n\nMethods\nThe study used an anonymous web‐based survey developed by a group of physicians, psychologists and researchers who work with individuals with DS, ASD and DS + ASD. The survey queried clinicians from various specialties about their practice patterns regarding assessment of suspected ASD in individuals with DS. The survey inquired about treatment recommendations for DS + ASD and perceived barriers to connecting families with evaluations and services. Data analysis involved descriptive statistics and Mann–Whitney U tests.\n\n\nResults\nMost respondents believe diagnosing ASD in individuals with DS significantly impacts management. Challenges were reported in accessing diagnostic evaluations, with heavy reliance on highly specialised DS and ASD clinics. Communication impairment (n = 64, 65%), aggressive behaviours (n = 38, 39%), self‐injurious behaviours (n = 33, 34%) and adaptive skills (n = 27, 28%) are priority targets for intervention, and applied behavioural analysis (ABA) (n = 80, 82%), speech therapy through insurance (n = 60, 61%), augmentative and alternative communication evaluation through insurance (n = 59, 60%), and occupational therapy through insurance (n = 57, 58%) are the most frequent referrals following a diagnosis of DS + ASD. All respondents identified multiple barriers to care for individuals with DS + ASD, including waitlists, insurance networks and requirements, lack of experienced providers and high turnover.\n\n\nConclusion\nThis study highlighted the complexity of caring for individuals with DS + ASD, revealed the heterogeneity of practice patterns among providers, and reported multiple barriers to care for this underserved patient population. Results should prompt work aimed at redressing barriers to care and additional research in the field of effective interventions for individuals with DS + ASD.\n\n"]