In 120 Stage I-IV testicular diffuse large B-cell lymphoma (DLBCL) patients treated from 1964 to 2015, we assessed the benefits of prophylactic contralateral testicular radiation (RT) and prophylactic central nervous system (CNS) therapy on overall, progression free, testicular relapse free, and CNS relapse free survival (OS, PFS, TRFS, and CRFS, respectively). Seventy percent of patients received RT, 53% received anthracyclines and rituximab (modern therapy), and 61% received CNS prophylaxis. On univariate analysis RT was associated with improved TRFS, PFS, and trended toward improved OS. On multivariate analysis (MVA), RT was significantly associated with improved OS and PFS; the PFS benefit persisted among patients receiving modern therapy. CNS prophylaxis was associated with improved OS, PFS, and TRFS, but not CRFS on univariate analysis, and was not significant on MVA. RT is associated with improved survival, and should be considered for all testicular DLBCL patients, but additional strategies are needed to prevent CNS relapse.