Adenomyoma is a benign gynecologic condition affecting women in their late reproductive years. Common clinical presentations include pain, particularly dyspareunia and dysmenorrhea, abnormal uterine bleeding, and infertility. Majority, however, may be asymptomatic. Various presentations of adenomyoma have been written in the literature, but exophytic subserosal growths have rarely been reported. More commonly, it involves the endometrium with invagination into the myometrium. We present a rare case of a primary subserosal pedunculated adenomyoma with no evidence of adenomyosis in a nulligravid premenopausal woman who underwent a uterine-sparing surgery and an extensive colonic resection with colostomy.