Autistic adults commonly experience anxiety and worry, although knowledge on how worry presents and the content, extent, and experiences among autistic adults is limited. A convergent parallel mixed-methods approach was used to explore the presentation and experiences of worry in autistic and non-autistic adults. Quantitative surveys were used to compare the content and extent of worry in autistic adults to non-autistic adults, with semi-structured interviews also conducted with autistic adults to gain a deeper understanding of the experiences, impacts and content of worry in autistic adults. Findings indicated that autistic adults demonstrated clinically significant levels of worry which were substantially higher than non-autistic adults. Autistic adults described worry as a cycle of negative thoughts impacting their daily life. Findings indicate that autistic adults may worry more than non-autistic adults, impacting on participation in activities of daily living, sleep, and mental health.