Background. Prolactinomas are benign pituitary tumors that frequently occur in women aged 20 to 50 years. Pituitary adenomas in children and adolescents are rare, and prolactinomas are the most common secretory tumors in this population. As in adults, prolactinomas are predominant in girls. The symptoms are heterogeneous, and differ according to sex, tumor volume, age of onset, and the prolactin level. Methods. We report a case of prolactinoma presenting as delayed puberty and review the literature on prolactinomas in young populations. Results. An 18-year-old male presented to our hospital with delayed puberty. Physical examination revealed underdeveloped pubic hair and genitalia. Laboratory data showed a high prolactin level and low testosterone level, and a bone age survey revealed a bone age of 14 years. Magnetic resonance imaging of the sella revealed a pituitary tumor approximately 1.8 cm in diameter, with a stalk deviating to the right side of the brain. Following cabergoline treatment, the prolactin level decreased in the first month and testosterone became normal after 3 months of treatment. The patient’s secondary sexual development improved gradually. Conclusion. Medical treatment with cabergoline exhibited favorable efficacy in controlling clinical symptoms and signs, and is safe for use in young populations.