Purpose: To examine the risks of postoperative nausea and vomiting (PONV) in breast cancer patients. Design: Descriptive, cross-sectional study. Methods: The study was conducted in the surgical oncology department of a tertiary hospital between June 2020 and December 2020. A total of 83 female patients who were scheduled for surgical treatment for breast cancer were included in the study. The patients were evaluated using the Patient Evaluation Form created by the researcher by scanning the literature, the VAS Pain Rating Scale, and the Apfel Risk Scoring System. Findings: A significant relationship was found between age and PONV at the 2nd, 4th, 8th, 24th and 48th hours after surgery (respectively: P = .00, P = .00, P = .00, P = .00, P = .00). There was a significant correlation between the duration of surgery and PONV at 0 hour, PONV at first oral intake and PONV at 4 hours (respectively; P ˂ .01, P ˂ .01). The highest rate of PONV of all time (50.6%) at the 0th hour when the VAS scores of the patients was the highest. The PONV rate at the 48th hour was the lowest of all time periods (1.2%) (respectively; P ˂ .01, P ˂ .01). Conclusions: While women with breast cancer who have undergone mastectomy have the highest risk of postoperative and nausea vomiting in terms of age and pain severity, the duration of the operation and the first oral intake time also pose a risk. Nurses play a key role in the quality of care, patient safety, and patient satisfaction. It is recommended that institutions create evidence-based strategies and take necessary precautions in the preoperative evaluation of patients in terms of postoperative nausea and vomiting.