Testicular/paratesticular mucinous cystadenoma is a rare type of ovarian epithelial tumor. This paper reported a patient with enlarged left testicle , and CT showed a multifocal cystic mass in left testis. Radical left testis orchiectomy was performed, and the pathology showed testicular borderline mucinous cystadenoma. The patient was followed up for 3 years and no recurrence and metastasis was observed.