Autistic people have described autistic burnout as an intense experience of physical, emotional, mental and social exhaustion impacting their ability to complete everyday tasks and contributing to poorer well-being. To identify and measure autistic burnout in practice and research, we need a self-report measure that gives accurate and consistent results. In this study, 379 autistic adults completed a recently developed measure of autistic burnout online, the AASPIRE Autistic Burnout Measure. We analysed their ratings to determine whether the measure is reliable (i.e. ratings are consistent), valid (i.e. the tool measures what it says it measures), correctly identifies those currently experiencing burnout, and is associated with other relevant experiences, such as camouflaging, anxiety and depression. The Autistic Burnout Measure was found to be reliable and valid. Autistic adults reporting greater autistic burnout also reported more camouflaging, autistic traits and greater general burnout, depression, and anxiety. The Autistic Burnout Measure was accurate in identifying individuals who reported currently experiencing autistic burnout and those who did not. Overall, our findings suggest that the Autistic Burnout Measure may be suitable for use in research and practice to identify and better understand experiences of autistic burnout.