Background In the UK, GPs play a key role in the identification and management of children, young people, and adults on the autism spectrum, but there is a paucity of research on GPs' perceptions of working with these patients. Aim To understand GPs' perceived self-efficacy in identifying and managing their patients on the autism spectrum, and the factors affecting this. Design and setting An online self-report survey was developed for completion by GPs across the UK. Method A total of 304 GPs in the UK took part. The survey collected responses on participants' background, training, and experience, both as a GP and with regard to autism, and included a 22-item knowledge of autism questionnaire, a 14-item self-efficacy scale targeting GPs' perceived confidence in identifying and managing their autistic patients, and an open question eliciting participants' experiences of working with autistic people. Results In total, 39.5% (n = 120) of GP participants reported never having received formal training in autism. Despite demonstrating good knowledge of its key features, participants reported limited confidence in their abilities to identify and manage autistic patients, with many citing a number of barriers that overwhelmingly focused on perceived failings of the current healthcare system (such as a lack of clarity around referral pathways). Conclusion There is an urgent need for improved local specialist service provision alongside clearer referral pathways for diagnosis to improve both GPs' confidence in caring for their autistic patients and the healthcare experiences of autistic patients and their families. Local clinical commissioning groups are best served to assist GPs in ensuring that they can reliably detect the condition and make appropriate provisions for support.