The serous papillary cystadenoma of low malignant potential in the paratesticular tissue is a tumor characterized by its resemblance to ovarian serous papillary tumor of low malignant potential. Several possible origins have been proposed but it is thought to originate from the Mullerian-type epithelium just like ovarian serous tumor of low grade malignancy. Because of the rarity of this tumor, the natural history and treatment have not been established. Herein we report on a serous papillary cystadenoma arising in the paratesticular tissue of a 12 year old . To our knowledge, this is the first reported case in the Korean literature. The size of this cystic tumor in this patient was 0.9x0.9x0.8 cm and had a sponge-like cut surface. The papillary structure was lined by both ciliated and nonciliated secretory cells, the same cellular structure as the salpinx. Areas with just a few mitoses and stratification of epithelial cells were noted, but invasion into the paratesticular tissue was absent, suggesting borderline malignancy. He is doing well after 5 months follow up. Prognosis of this scrotal tumor is thought to be better than the ovarian tumor of similar histology due to a better possibility of early detection.