Objective. To assess the effects of an 8-week stress management and health promotion program on women undergoing breast cancer chemotherapy treatment. Patients and methods. A total of 61 patients were recruited in 2 cancer centers and were randomly assigned to the intervention program (n = 30) or control group (n = 31). The intervention program consisted of different stress management techniques, which were combined with instructions for lifestyle modification. Assessments were carried out through questionnaires and measurement of body mass index (BMI) at baseline and at the end of the 8-week program. Results. In all, 25 participants completed the intervention program, whereas 28 participants completed the observational control program. The intervention program resulted in a small effect size on internal dimension of Health Locus of Control (HLC) and a medium effect size on stress, depression, anxiety, night sleep duration, and chance dimension of HLC. A strong effect size was recorded for BMI and sleep onset latency. Self-rated health, spiritual well-being, and powerful others dimension of HLC were not significantly affected. Additionally, some of the participants reported a reduction in the side effects caused by chemotherapy. Conclusions. The intervention resulted in several benefits for the general health status of patients. Therefore, it should be considered as feasible and potentially beneficial for women undergoing breast cancer chemotherapy. However, it is necessary for this intervention to be tested through a randomized controlled trial in a larger sample of patients before adopting this program in standard cancer care.