Interventions based on functional assessments, particularly functional analyses (FAs), are more likely to be effective relative to interventions that are not function-based. However, few clinical investigations have used FAs to assess operant vomiting. This is notable given that operant vomiting represents a medically serious form of problem behavior. To the degree that clinicians can conduct FAs, and use those results to inform function-based treatments for operant vomiting, they can reduce behavior that is associated with considerable medical risk and is also socially conspicuous and stigmatizing. In the current study, we conducted an FA of operant vomiting in a young male with high-functioning autism spectrum disorder. Results suggested operant vomiting was maintained by access to adult attention and escape from academic demands, which is noteworthy given that vomiting is often hypothesized to be maintained by automatic reinforcement. We then implemented a function-based intervention to achieve clinically significant reductions in operant vomiting.