Abstract : Breast cancer chemotherapy is associated with a decline in measured cardiorespiratory fitness and increased fatigue. Physical activity has emerged as a feasible intervention to limit these side effects. Quantitative evaluation is necessary to propose a better-adapted physical activity and to evaluate efficacy. We undertook a prospective study to assess the effects of a home-based adapted physical activity (APA) program on aerobic capacity, strength, and fatigue in women treated with adjuvant or neoadjuvant chemotherapy for breast cancer versus usual care. This was an open two-arm, randomized controlled trial. Study included outpatient groups in the Department of Physiology and Medical Oncology, at Limoges University Hospital, France. Forty-four patients treated with adjuvant or neoadjuvant chemotherapy for breast cancer. Patients were randomly assigned to a control group or an APA group. Intervention consisted of a 3-week, home-based, supervised, combined APA program (endurance and resistance training) during 27 weeks. The primary endpoint was cardiopulmonary function assessed by maximal peak oxygen consumption (VO2peak). Secondary endpoints included a 6-minute walking test (6MWT), and assessment of muscular strength, fatigue, quality of life, physical activity level, and anxiety/depression. At 27 weeks, VO2peak increased by 1.83 ± 0.68 ml.min-1.kg-1 in the APA group (P =0.009) and decreased by 1.31 ± 0.65 ml.min-1.kg-1 in the control group (P = 0.046). The difference between the two groups was not significant (2.26 ± 1.53 ml.min-1.kg-1, P = 0.140) in intention-to-treat analysis, but it was significant in per protocol analysis (3.49 ± 1.64 ml.min-1.kg-1, P = 0.049). At 27 and 54 weeks, no significant differences were observed between the two groups for the cardiopulmonary exercise test, 6MWT, quadriceps strength, or quality of life. In breast cancer patients, a home-based supervised program during chemotherapy and radiotherapy treatment may be safe, feasible and increase VO2peak. In this study, heavy evaluation tests explain patient's non-adherence and do not permit to obtain statistically significant results between APA and control groups. aerobic home-based adapted physical activity is beneficial on aerobic capacity.