Recognizing higher rates of co-occurring health conditions in autistic adults and the frequent use of hospital-based health care services, this study compared rates of repeat emergency visits, repeat hospitalizations, and delayed discharges in autistic adults to other adults with and without developmental disabilities matched for age and sex, living in Ontario, Canada. Returning to the hospital emergency department within a month, being readmitted to hospital within a month and experiencing a delayed discharge from hospital were each more likely to occur in autistic males and females than their counterparts without developmental disabilities, with the risk ratios being the highest for delayed discharges. Males and females with other developmental disabilities were more likely to return to the emergency department within a month than their autistic counterparts, and males with other developmental disabilities were more likely than autistic males to be readmitted to hospital, but the likelihood of delayed discharge in the two groups was similar. These findings suggest that more needs to be done to both improve hospital-based experiences of autistic adults and adults with other developmental disabilities, and to strengthen community-based care to reduce the likelihood of repeat and extended stays in hospital.