We present a case of a middle-aged male Chinese patient who was asymptomatic with a large (6×7cm) right adrenal mass was found in this patient upon routine health examination. He underwent laparoscopic right adrenalectomy after comprehensive evaluation, and the mass was finally diagnosed as right adrenal endothelial (vasculature) cyst associated with adrenocortical adenoma according to pathological and immunohistochemical studies. The puzzling image resemblance of a variation of adrenal cyst to carcinoma necessitated histological examination for confirmative diagnosis. The development of endothelial cyst is extremely rare, and its association with other adrenal neoplasms is even rarer. Herein, we report a new case of adrenal endothelial cyst associated with adrenocortical adenoma, which was almost indistinguishable from adrenocortical carcinoma, and hope that it would be helpful in the diagnosis of other similar cases.