The psychosocial outcomes of individuals with high-functioning autism spectrum disorder (HFASD) appear to be diverse and are often poor relative to their intellectual or language level. To identify predictive variables that are potentially ameliorable by therapeutic intervention, this study investigated self-reported psychosocial quality of life and associated factors for adults with HFASD. All participants (n = 154) had a diagnosis of autism spectrum disorder, were over 18 years of age, lived in the community, and had used one or more support services during the survey period. The results demonstrated that psychosocial quality of life was lower than that of the general Japanese adult population. Environmental factors, such as mother’s support and early diagnosis, were associated with better quality of life, and aggressive behaviors were associated with poorer quality of life, while expressive language level at preschool years, a conventional outcome predictor, did not predict quality of life. These results emphasize that quality of life measures should be included as outcome indicators in treating individuals with HFASD.