This comparative effectiveness trial examined the effects of a behavior change intervention supplemented by a general or specific exercise recommendation on physical activity among postpartum mothers. Participants (N = 49) attended three workshop sessions that provided the exercise recommendation and taught self-regulatory skills. Physical activity, self-efficacy, planning, and barriers were assessed at baseline, post-intervention, and 6-month follow-up. Self-reported physical activity increased significantly in both groups (p < .001), but the increase was larger in the general condition (p = .03). Both groups reported increased planning and decreased barriers. Postpartum mothers may benefit from interventions that teach strategies for overcoming barriers while allowing them to choose preferred activities.