Individuals with autism spectrum disorders (ASD) spend the majority of their lives as adults, and psychosocial interventions show promise for improving outcomes in this population. This research conducted a systematic review of all peer-review studies evaluating psychosocial interventions for adults with ASD. A total of 1,217 studies were reviewed, only 13 met inclusion criteria. The majority of studies were single case studies or non-randomized controlled trials, and most focused on applied behavior analysis or social cognition training. Effects of psychosocial treatment in adults with ASD were largely positive ranging from d = 0.14-3.59, although the quantity and quality of studies is limited. There is substantial need for the rigorous development and evaluation of psychosocial treatments for adults with ASD.