Primary renal mucinous cystadenocarcinoma is a very rare lesion of kidney which originates from the metaplasia of the renal pelvic uroepithelium. Only one case with primary mucinous cystadenocarcinoma has been reported in the English literature. We report second case of mucinous cystadenocarcinoma which was radiologically classified as type-IIF Bosniak cyst in peripheral localization. We aimed to present this extreme and unusual entity with its radiological, surgical, and pathologic aspects under the light of literature.