Effective treatments of highly prevalent stress-related outcomes such as depression and anxiety are understudied in adults with autism spectrum disorder (ASD). A randomized controlled trial with baseline, post-intervention, and 10-week follow-up, that explores the effects of animal assisted therapy (AAT) was conducted. In total, 53 adults with ASD with normal to high intelligence were randomized in an intervention (N = 27) versus waiting list control group (N = 26). The remarkable adherence to the therapy program by study participants and the program's clinically relevant effects indicate that AAT with dogs can be used to reduce perceived stress and symptoms of agoraphobia, and to improve social awareness and communication in adults with ASD with normal to high intelligence.