A surgical case of proliferative funiculitis (pseudosarcomatous myofibroblastic proliferation of the spermatic cord) with a prominent mast cell infiltration is reported. A 67-year-old man with a history of right inguinal herniorrhaphy 7 years earlier was operated on for diffuse swelling of the inguinal region and scrotum. A large lipoma was found in the inguinal region, and a nodular lesion, measuring 2.7 cm in maximal dimension, was firmly attached to the right spermatic cord. The nodular lesion showed diffuse proliferation of fibroblasts and myofibroblasts associated with the deposition of collagen. A diffuse infiltration of numerous mast cells was found throughout the lesion. Lesions that belong to the group of inflammatory pseudotumors are rarely accompanied by a prominent mast cell infiltration, and the differentiation from mast cell neoplasms is often problematic in such cases. The present case is the first example of proliferative funiculitis associated with this rare phenomenon.