Background: Juvenile breast hypertrophy is uncommon and is characterized by excessive breast enlargement in the peripubertal period. The clinical entity is thought to result from increased sensitivity of mammary tissue to normal levels of circulating hormones. Case: Here, we report a female patient, aged 12 years and 6 months, suffering from juvenile breast hypertrophy, who presented at the third month of symptoms and benefited from tamoxifen treatment. Comments: In experienced clinics, use of tamoxifen in the treatment of juvenile breast hypertrophy during the brisk growth period may become a medical alternative to reconstructive surgery. © 2010 North American Society for Pediatric and Adolescent Gynecology.