Objective To provide some reference for clinical decision making in breast cancer patients during pregnancy by analyzing and discussing the process of drug treatment and pharmacological care of one patient.Methods A case of a pregnant breast cancer patient who underwent chemotherapy during pregnancy was analyzed and discussed based on evidence-based medicine in terms of chemotherapy indications, chemotherapy regimen selection and chemotherapy drug adjustment, antiemetic regimen, and pharmacological care of the patient.Results A treatment plan was developed for the patient based on evidence-based medicine. The patient completed five courses of chemotherapy with no significant adverse reactions and delivered a baby girl by caesarean section one month after the last chemotherapy. Both the patient and the baby were in good condition and the patient continued antitumor treatment after delivery.Conclusion Clinical pharmacists should give full play to their own advantages, provide individual pharmaceutical care for special patients, and reflect their value in multidisciplinary diagnosis and treatment.