Cystic lymphangioma of the adrenal gland is a rare tumor, which is often sub-clinical. Preoperative diagnosis is difficult. We present a case of a 47 year-old female in whom an incidental left cystic mass of 12 cm by 10 cm with no features of malignancy was discovered by ultrasound scan. A further computed tomography scan confirmed the ultrasound findings. Biochemical screening ruled out a secreting adrenal tumor. Because of the size of the cyst, the lesion was resected and the diagnosis of benign adrenal cystic lymphangioma was histologically confirmed. Computed tomography is the reference examination for delineating the topography and extent of the lesion, especially when it is large. Although imaging can characterize the cystic nature of a lesion, it sometimes fails to establish a specific diagnosis, so surgery or fine needle aspiration should be done for a definitive diagnosis. The characteristic features of cystic adrenal lymphangioma are discussed together with a review of the recent literature.