After surgery, breast cancer patients are offered adjuvant chemotherapy to avoid cancer cell spread. During chemotherapy process, neutrophils could fall relatively, and side effects could spike to the peak. Therefore, the medical care personnel should prevent the progression of the side effects. This study aimed to examine the effects of Chan-Chuang qi-gong therapy on complete blood counts in breast cancer patients treated with chemotherapy. This study used a quasi-experimental design. The experiment group (n = 32) received a 21-day Chan-Chuang qi-gong therapy, whereas the control group (n = 35) did not. White blood cells, platelet, and hemoglobin were measured on the day before chemotherapy and on days 8, 15, and 22 during chemotherapy. According to this study, there were significant differences in white blood cells (F = 115.76, P <.001), platelets (F = 25.29, P <.001), and hemoglobin (F = 15.39, P <.001) over the 3-week therapy between the experiment and control groups. Chan-Chuang qi-gong therapy may decrease leukopenia in breast cancer patients treated with chemotherapy. It is recommended conducting more studies on qi-gong and then introducing it in clinical nursing practice at an appropriate time to promote quality of nursing care and quality of patient life.