Young adults with autism spectrum disorder (ASD) experience increased rates of anxiety and depression which can impact academic success. The Stepped Transition in Education Program for Students with ASD (STEPS) applies cognitive-behavioral principles to help young adults with ASD improve their adjustment to postsecondary education. We aimed to determine if STEPS had an effect on anxiety and depression. Treatment-seeking adults with ASD (n = 32; Mage = 19.74) were randomized to STEPS or transition as usual (TAU; i.e., waitlist control group). STEPS participants evinced significantly greater declines in depressive symptoms from pre-treatment to post-treatment compared to the waitlist. Anxiety symptoms did not significantly change. Results suggest that transition support for young people with ASD may improve mental health.