Students with high-functioning autism spectrum disorder (HFASD) may have difficulties with writing despite average or above-average intellectual ability. We designed an intervention strategy (Draw, Sentence, Detail, Check) to improve the ability of an 8-year-old with HFASD to write elaborated sentences in response to written prompts. We investigated the effectiveness of the strategy using a single-subject A-B-A design. Results indicated that the student's written responses were longer and contained more details after the treatment and that gains were maintained 10 weeks later. Here we consider the intervention strategy and findings from a social cognitive perspective. We discuss theoretical and instructional implications as well as suggestions for future research.