Prepubertal gynecomastia due to testis tumors is a very rare condition. Nearly 5% of the patients with testicular mass present with gynecomastia. Sertoli cell tumors are sporadic in 60% of the reported cases, while the remaining is a component of multiple neoplasia syndromes such as Peutz-Jeghers syndrome and Carney complex. We present a 4-year-old boy with gynecomastia due to Sertoli cell tumor with no evidence of Peutz-Jeghers syndrome or Carney complex.