Background: Moderate weight loss and physical activity (PA) can prevent or delay type 2 diabetes however there is a need for innovative, effective programs to promote PA in high-risk individuals. Purpose: We examined the effect of a group-based adaption of the DPP lifestyle intervention implemented in partnership with the YMCA (YDPP) on changes in moderate-vigorous physical activity (MVPA) in economically disadvantaged adults with prediabetes. The effects of psychosocial and community-level factors were explored. Methods: Participants were randomly assigned to YDPP or brief counseling. Accelerometer data from 216 participants were used to identify: 1) change in MVPA and 2) sedentary behavior over 24 months. Results: YDPP had no significant effect on either outcome. Baseline PA and crime were associated with less MVPA while higher perceived health and green space were associated with more MVPA over time. Baseline sedentary behavior, perceived health, and green space were inversely related to being sedentary. Discussion: Results suggest that changing dietary and PA behaviors simultaneously may adversely affect changes in PA. Translation to Health Education Practice: Additional research is needed to determine the preferred format for PA interventions. Peer mentoring should be considered. Research is needed to identify valid accelerometer cut points in sedentary, overweight adults.