Using Piper's Integrated Fatigue Model, this research project was planned to determine the level of fatigue experienced by Turkish women with breast cancer undergoing adjuvant chemotherapy, to discover the factors affecting fatigue, and to provide a reference by means of which an effective nursing care for such patients could be planned. In assessing the level of fatigue and factors affecting it, a patient information form, the Piper Fatigue Scale, and the Rotterdam Symptom Checklist were used. The reliability tests performed afterwards showed that the scales are appropriate tools for use in Turkish women with breast cancer. Before treatment, psychological symptoms' distress was higher than physical symptoms' distress. However, following treatment, the latter was found to be closer to the former. When pretreatment and posttreatment physical and psychological symptoms were compared, it was noticed that fatigue, nausea, anorexia, vomiting, constipation, depression, and loss of hope for the future were among the symptoms observed to increase the most in the posttreatment period. Different from the other studies, we determined that all of the patients experienced fatigue 7 to 10 days after the chemotherapy cycle and the sensory/affective fatigue scores were high. Breast cancer patients undergoing chemotherapy experienced a moderate level of fatigue, which was influenced by level of income, stage of disease, and symptoms related to chemotherapy, showing compliance with similar studies. Following up patients individually and keeping the treatment-related symptoms under control were noticed to help prevent fatigue.