During dissection of the thoracoabdominal region of a 56-year-old male cadaver, we encountered three sternalis muscles (one on the right side, two on the left side) covered by superficial fascia and located anterior to the pectoralis major muscle. Additionally, abnormal attachment of the pectoralis major muscle was also observed. We think that the existence of the sternalis muscle and abnormal attachment of the pectoralis major muscle should not be overlooked in the surgical and diagnostic procedures.