Purpose: We previously reported the effectiveness of a 12-week physical activity behavior change intervention for breast cancer survivors postintervention with this report, aiming to determine delayed and/or persistent effects 3 months after intervention completion. Methods: Forty-one sedentary women with stage I, II, or IIIA breast cancer currently receiving hormonal therapy were randomly assigned to receive the 12-week Better Exercise Adherence after Treatment for Cancer intervention or usual care. Assessments occurred at baseline, postintervention, and 3months postintervention. Results: Weekly minutes of greater than or equal to moderate intensity physical activity measured by accelerometer showed a significant group by time interaction (F = 3.51; P = 0.035; between group difference in the mean change from baseline to 3 months postintervention, 100.1 minute, P = 0.012). Significant group by time interactions also showed sustained improvements from baseline to 3 months postintervention in strength (F = 3.82; P = 0.027; between group difference, 11.2 kg; P = 0.026), waist-to-hip ratio (F = 3.36; P = 0.041; between group difference, -0.04; P = 0.094), and social well-being (F = 4.22; P = 0.023; between group difference, 3.9; P = 0.039). A delayed reduction in lower extremity dysfunction 3 months postintervention was noted (F = 3.24; P = 0.045; between group difference in the mean change from postintervention to 3 months follow-up; P = -7.6; P = 0.015). No group by time effect was noted for fitness, body mass index, percent fat, bone density, total quality of life (Functional Assessment of Cancer Therapy-General), fatigue, endocrine symptoms, cognitive function, or sleep. Conclusions: The intervention resulted in sustained improvements in physical activity, strength, central adiposity, and social well-being with lower extremity function benefits appearing 3 months after intervention completion. Testing translation in a multisite study is warranted. Copyright © 2009 American Association for Cancer Research.