Objectives: To determine the feasibility and preliminary effectiveness of a group dynamics–based exercise intervention versus a personal training intervention for increasing physical activity (PA), physical fitness, and quality of life (QOL) in post-treatment breast cancer survivors. Sample & Setting: 26 women with stage I or II breast cancer who attended intervention activities at a local academic institution. Methods & Vriables: Participants were randomly assigned to receive an eight-week intervention in either a group dynamics–based exercise or a personal training setting. Both intervention arms received supervised exercise twice per week, as well as PA education and discussion sessions. Results: Significant increases were noted in both intervention arms for vigorous PA, chest press, and leg press. Increases in overall QOL and total PA were significant only in the group dynamics–based exercise intervention arm. Implications for Nursing: The group dynamics–based exercise intervention produced similar improvements in PA and physical fitness compared to the personal training intervention, and it may have facilitated greater improvements in overall QOL.