Many autistic people cite a strong attachment to animals, and some studies suggest they may even show a bias towards animals over people. This mixed-methods study explored companion animal attachment in the adult autistic community. In a quantitative study with 735 people, we found that autistic adults were equally attached to their pets as neurotypicals but were less likely to own them, even though pet ownership corresponded with better mental health outcomes. Substituting pets for people also served as a compensatory mechanism for social contact in the autistic sample. In a second qualitative study, we explored the lived experiences of 16 autistic pet owners. The interpretive phenomenological analysis highlighted the benefits and the barriers to animal companionship. Together these mixed methods findings underline how pets improve the lives of their autistic owners. We conclude with specific recommendations for increasing animal companionship opportunities for autistic adults.