BACKGROUND Galactoceles have been previously described as an unusual cause of benign breast enlargement in male infants and children. METHODS A 3-year-old prepubertal girl presented with a right-sided breast mass and was found to have a 4.4-cm hypoechoic cyst on ultrasound imaging with otherwise normal endocrine studies including prolactin levels. She underwent cyst aspiration which revealed milky fluid. Fat globules were identified with microscopic examination, confirming the diagnosis of a galactocele. Aspiration resolved the mass. CONCLUSIONS The etiology of galactoceles in nonlactating women is poorly understood. Traditionally, treatment of these benign cysts in male children has been surgical excision. In prepubertal girls, conservative management by surveillance or needle aspiration is warranted to prevent damage to developing breast tissue.