The prognostic significance of tumor-infiltrating lymphocytes (TILs) has been studied recently in many cancers. For the first time in a nonendemic region, we have evaluated the prognostic value of TILs in a whole population–based nationwide cohort of nasopharyngeal carcinoma (NPC) in Finland. A total of 115 cases from Finnish hospitals were included. TILs were analyzed using hematoxylin and eosin–stained slides according to the criteria of the International Immuno-Oncology Biomarker Working Group. TILs were evaluated separately in stromal and tumor compartments. The log-rank test and univariable and multivariable analyses were used to compare survival in patients with tumors with low and high TILs. A significant positive correlation was observed between the occurrence of intratumoral and stromal TILs (P < .001). In multivariable analysis, NPC cases with low intratumoral TILs had poor overall survival with a hazard ratio (HR) of 2.55 and 95% confidence interval (95% CI) of 1.60 to 4.05 (P < .001). Cases with low intratumoral TILs also had poor disease-specific survival (HR, 2.02; 95% CI, 1.16-3.52; P = .015). Keratinized tumors with low intratumoral TILs were associated with an even poorer overall survival (HR, 3.94; 95% CI, 2.17-7.15; P < .001) and a poor disease-specific survival (HR, 2.97; 95% CI, 1.46-6.05; P = .009). Our study demonstrates that the evaluation of TILs is simple and can be assessed routinely in NPC.