The present study reported on the case of a 60-year-old postmenopausal female who suffered from fatigue and was diagnosed with a right-sided BC tumor....the patient received RC48 as the third-line therapy and achieved a durable and effective clinical response. To date, the patient has benefited from 12 cycles of RC48 without any severe adverse effects. The overall survival was >3 years. The present study showcased that RC48 was effective and tolerable for a patient with HR- and HER2-positive BMBC.