This research compared the written compositions of 16 adults with high-functioning autism spectrum disorders and 16 neurotypical control participants, and examined the influence of theory of mind on their writing. Participants ranging in age from 17 years to 42 years, matched on Vocabulary subtest scores from the Wechsler Adult Intelligence Scale (1997), completed the Social Attribution Task and wrote an expository and a narrative text. Texts were assessed on 18 variables representing quality, mechanics, and length. It was found that adults with HFASD wrote lower quality narrative and expository texts, and narratives of shorter length. Theory of mind was positively associated with writing quality and text length across both genres.