Testicular lymphoma is a rare disease, accounting for 1-2% of non-Hodgkin lymphoma and 5-9% of all testicular tumors, and has a high relapse rate with a poor prognosis. We report a patient with testicular diffuse large B-cell lymphoma (DLBCL) who relapsed after being in remission for 16 years. He had undergone orchiectomy of the right testis and was diagnosed as having DLBCL (stage IAE) at 49 years of age. After 3 cycles of CHOP, he achieved a complete remission. Orchiectomy was performed because of a left testicular tumor, and he was again diagnosed with DLBCL at the age of 65. VH3-21 was detected in lymphoma cells at the times of both the first diagnosis and the relapse based on analysis of the variable region of the immunoglobulin heavy chain. Accordingly, the lymphoma cells at relapse were confirmed to be the same clone as that which had been documented at the first diagnosis.