Background: Although disparities in mental health and subjective quality of life have been reported for autistic adults, reasons for these disparities are poorly understood. A potential factor in these disparities is exposure to social stressors related to minority status (i.e., minority stress), including stigma and discrimination. Autistic individuals are more likely than non-autistic individuals to possess other minority identities, including sexual minority identities. However, to date, few studies have examined whether sexual minority autistic adults experience diminished mental health relative to heterosexual autistic adults, and no research has examined subjective quality of life for sexual minority compared to heterosexual autistic adults.Methods: Participants were 679 autistic adults aged 18.5 to 83.3 years recruited through Simons Powering Autism Research Knowledge Research Match. Participants completed surveys online, including measures of anxious and depressive symptomatology, perceived stress, and subjective quality of life. Participants reported their sexual orientation and other socio-demographic variables. Results: A large proportion of autistic adults reported a sexual minority identity (43.4%). Sexual minority autistic adults showed poorer mental health and lower subjective quality of life relative to heterosexual autistic adults. Diminished quality of life in the sexual minority group appears to be driven by the strength of the effects for gay and pansexual compared to heterosexual autistic adults. Conclusion: Understanding factors that may be related to poorer mental health and decreased subjective quality of life in autistic adults is critical and has been identified as a research priority among autistic stakeholders. The findings reported here underscore the need to examine mental health and subjective quality of life disparities among autistic individuals within a societal context, taking into consideration the potential of intersecting minority identities and increased social stressors, as these hold the potential to increase risks for poorer outcome.