Objective · To investigate the impact of body weight and physical activity during different stages of adjuvant chemotherapy on the quality of life after chemotherapy among breast cancer patients. Methods · In a convenient sample of breast cancer patients with no prior history of systemic therapy, physical activity and quality of life were measured with anthropometric measurements, international physical activity evaluation questionnaire and Chinese version of functional assessment of cancer therapy-breast (FACT-B) scale before, during and after chemotherapy. Data was processed using repetitive measurement variance analysis and correlation analysis. Results · Among the 140 breast cancer patients, the average incidence of obesity during chemotherapy was 30.24%. An increase of body mass index (BMI) was observed throughout the treatment course. During adjuvant chemotherapy, the median physical activity was 844.50 (MET·min)/week. Obesity before chemotherapy was significantly negatively correlated with quality of life among patients receiving adjuvant chemotherapy (r-0.21, P0.014), while physical activity energy consumption was positively correlated with quality of life (r0.20, P0.019). Conclusion · Obesity and insufficient physical activity are rather common during adjuvant chemotherapy treatment in breast cancer patients, and they are strongly correlated with patients quality of life after chemotherapy.