Cancer-related fatigue is the most disabling symptom experienced by breast cancer patients following the cancer treatment. The positive effects of physical activity in the rehabilitation of breast cancer patients are documented in several studies. In a randomized controlled study the effects of a structured physical training program on fatigue and health-related quality of life were evaluated. Patients and Methods: 63 breast cancer patients with cancer-related chronic fatigue were randomized at the beginning of the inpatient rehabilitation. The control group received the standard complex rehabilitation program, the intervention group a structured physical training program and additional muscle strength and aerobic exercises. The effects of the treatment were evaluated by questionnaires at the start of rehabilitation (t1), end of rehabilitation (t2), and 3 months after t2 (t3). Isometric muscle strength and aerobic capacity were evaluated at t1 and t2. Results: There was an improvement of muscle strength at the end of rehabilitation for both groups. The increase from t1 to t2 was significantly higher for the training group. The scores for global quality of life, physical well-being, and functionality increased from t1 to t2, but further improvement in the follow-up (t3) was only observed in the training group. The cancer-related fatigue was significantly reduced in the training group from t1 to t3, however, not in the control group. Conclusions: Structured physical training programs initiated during inpatient rehabilitation and continuously practiced in the time thereafter can improve symptoms of chronic fatigue and quality of life in breast cancer patients.