A 54-year-old man presented with the left inguinal swelling. The operation was performed with diagnosis of the hydrocele of spermatic cord. A tumor was 3.0 cm x 2.5 cm in size, cystic with yellowish serous fluid. After the operation, this tumor is diagnosed as mesothelial cyst through the histopathologic examination. This is a rare case, however it is worth to consider that there is a possibility to be a mesothelial cyst when the tumor has been found at the inguinal region.