Breast cancer is excessive cell proliferation that attacks the breast tissue. Breast cancer is a problem that requires serious attention, especially for women. Breast cancer is currently the first cause of death in women in the world. Nausea and vomiting caused by chemotherapy is one of the side effects that most often affects the quality of life of cancer patients undergoing chemotherapy. These side effects can be prevented by administering antiemetic drug therapy. Accuracy in the administration of antiemetic drugs will increase the safety and effectiveness of drug use. This study aims to evaluation of antiemetic treatment therapy based on the accuracy of drug selection, dosage and the resulting therapeutic effect. This study used a purposive sampling method by collecting data retrospectively, namely monitoring the use of antiemetics in breast cancer chemotherapy patients in the inpatient room of RSUD Dr. Pirngadi Medan. The results of this study obtained 20 patients who entered the inclusion criteria, seen as many as 100% of patients received antiemetics with appropriate doses, and as many as 100% of patients received the appropriate drugs.