Healthcare professionals play a vital role in identifying and supporting autistic people. This study systematically reviewed empirical research examining healthcare professionals' knowledge, self-efficacy and attitudes towards working with autistic people. Thirty-five studies were included. The included studies sampled a range of countries and professional backgrounds. A modified quality assessment tool found the quality of the included studies was moderately good. Narrative synthesis indicated that healthcare professionals report only moderate levels of autism knowledge and self-efficacy, and often lack training. Variation within and between countries and professional background was not explained by demographic factors. The reviewed evidence suggests health professionals' limited knowledge and self-efficacy in working with autistic people is a challenge to the provision of healthcare for autistic individuals.