Rationale:Adenomyoma of the broad ligament is rare. Owing to the absence of typical clinical signs and imaging methods, preoperative diagnosis is challenging, and it is mainly diagnosed through surgical pathology.Patient concerns:The patient experienced recurrent lower abdominal pain for 4 years. Treatments with traditional Chinese medicine and anti-inflammatory drugs were ineffective, and painkillers became less effective over time owing to resistance. Multiple ultrasounds revealed a mass in the right adnexa, but gynecological tumor markers were normal.Diagnosis:The preoperative diagnosis was unclear, but a mass in the right adnexa was suspected.Interventions:The patient underwent laparoscopic exploration, which revealed a 25 mm x 25 mm x 20 mm spherical mass on the anterior leaf of the right broad ligament. It had clear boundaries, a hard texture, and was not attached to the uterus, fallopian tube, or ovary. The mass was completely excised. Gross examination of the specimen revealed a disorganized cut surface with a small amount of coffee-colored fluid. Postoperative pathology confirmed it was an adenomyoma of the broad ligament.Outcomes:The patient's lower abdominal pain resolved after surgery, and follow-up has shown no recurrence of pelvic masses.Lessons:Adenomyoma of the broad ligament can cause recurring abdominal pain. Preoperative diagnosis is challenging, but laparoscopic surgery can confirm the diagnosis, remove the tumor, and relieve symptoms.