Complete antethoracic block for modified radical mastectomy is a composite block comprising the antethoracic medial, antethoracic inferior, and antethoracic lateral blocks. The puncture targets of all components are easy to identify, and the risk of complications such as pneumothorax is low. Our patient was a 72-year-old woman undergoing modified radical mastectomy for breast cancer. After induction of general anesthesia, but before surgical incision, she received a complete antethoracic block for anesthesia, which also provided good analgesia postoperatively. We believe that complete antethoracic block is suitable for postoperative analgesia in patients undergoing this surgery.