Primary retroperitoneal teratomas involving adrenal glands are exceedingly uncommon accounting for only 4% of all primary teratomas. They are more common in childhood and rarely occur in adults. Only a very few case reports have been documented in literature so far. Herein, we report a mature (benign) cystic retroperitoneal teratoma in the region of left adrenal gland in a 22-year-old otherwise healthy male patient who presented with a 1-month history of left flank pain. In addition, a literature review on teratomas is included.