Objective To report a rare case of unilateral complete absence of rectus abdominis muscle in an adult male without any other malformations, and reveal the abdominal dissection process, abdominal wall muscles and their blood supplies. Methods The abdominal wall muscles, their blood supplies, and innervations were dissected and observed. The development and morphology of rectus abdominis on both sides were compared. Results The cadaver had no rectus abdominis muscle on the right side. The superior and inferior epigastric arteries met with each other and remained intact in the substitutional connective tissue within the rectus sheath. The intercostal and subcostal nerves (T7-T12) pierced the sheath and reach the superficial fascia. The left rectus abdominis muscle was complete with compensatory hypertrophy. No scar or signs of surgery were found on the skin. No abdominal organ was absent, and no adhesion was found in the peritoneum except the liver area. Conclusion The absence of right rectus abdominis may result from abnormal embryonic development before the 6th week. Rectus abdominis flaps are used in many surgical reconstruction surgeries. The knowledge of the related mutations is clinically significant for preoperative preparation and the use of rectus abdominis flap.