Lipoma arborescens is an intraarticular lesion characterized by a frond-like mass of mature fat cells, usually involving the suprapatellar bursa. It is a rare lesion in adults and extremely rare in children. Because of the fatty nature of the lesion, the MRI findings of lipoma arborescens are specific. We present the MRI findings of lipoma arborescens of the knee in a 9-year-old girl.