BACKGROUND Paratesticular tumors are rare causes of scrotal masses; most are benign and arise from the spermatic cord. We present the case of a dermoid cyst, a rare benign paratesticular tumor mimicking a torsed supernumerary testis. CASE REPORT An 8-year-old male presented to the Emergency Department with intense pain and swelling in the left hemiscrotum. He reported severe stabbing pain in his left hemiscrotum, quantified as 10/10, and demonstrating no improvement with change in position. Ultrasonography of the scrotum showed an oval-shaped heterogeneous, predominantly hypoechoic structure observed immediately inferior and lateral to the left testicle, showing no internal vascularity. The right hemiscrotum showed no testicular structure. Based on the sonographic observations, the possibility of 2 adjacent testicles in the left hemiscrotum was raised; the one without vascularity and with hypoechoic texture suggested the presence of ischemic changes due to torsion. The differential diagnosis of a paratesticular mass includes a paratesticular tumor, mimicking of paratesticular neoplasms (i.e. polyorchidism and splenogonadal fusion) and metastases. Surgical exploration of the left hemiscrotum revealed a normal untorsed left testis with an adherent paratesticular mass. An intraoperative frozen biopsy of the mass offered the preliminary diagnosis of an epidermoid cyst. CONCLUSIONS Paratesticular tumors can clinically present variably as a mass, which can be painful. Dermoid cysts can present as a painful mass and the sonographic appearance varies from anechoic to hyperechoic according to the cyst contents. A dermoid cyst as the differential diagnosis of a painful paratesticular mass in boys is important along with the possibility of a torsed supernumerary testicle.