Interpretive ethnography was used as a framework to examine perceptions of physical activity behavior of 12 adults with mild mental retardation. Four parents and two job supervisors also agreed to participate. Multiple data sources included in-depth interviews, diaries, accelerometry, and informal observations. Participants reported many physical activity barriers, benefits, and leisure choices similar to the general population; however, two particularly salient themes related to negative influences and lack of guidance from support systems were apparently unique to this group. Results suggest that (a) adults with mental retardation need specially designed physical activity education and training programs and (b) supports system providers should be educated regarding the importance of physical activity to health for these individuals.