Adults with autism spectrum disorder (ASD) have lower engagement in their communities, higher rates of unemployment/underemployment, and continued difficulties with challenging behavior than their neurotypical peers. 5 waves of data were collected at 3-month intervals. Families in the intervention condition participated in an intervention during the 6 months between baseline and time 3 data collection, the waitlist control condition received the intervention immediately after the time 3 data collection. The results indicated medium to large effect sizes associated with the Working Together intervention across critical outcomes, including adults on the spectrum experiencing significant increases in meaningful activities and decreases in internalizing problems. However, increases in work-related activities were not statistically significant and the observed first-half of a standard deviation difference from before to after the intervention indicated clinically substantial change. It was also found that maintenance of the treatment effect through 6 months post-treatment for the intervention group and replication within the control group after they received the intervention. Working Together is a multi-family group psychoeducation intervention designed to improve functioning during adulthood. These findings highlighted the need for more intervention services research during adulthood and specifically family-centered support.