The Glasgow Prognostic Score (GPS), an inflammation-based prognostic score including C-reactive protein and albumin, shows significant prognostic value in several types of solid tumors. The prognostic value of GPS in lymphoma remains unclear. We performed this study to evaluate the prognostic significance of GPS in extranodal natural killer (NK)/T-cell lymphoma (ENKL). We retrospectively analyzed 164 patients with newly diagnosed ENKL. The prognostic value of GPS was evaluated and compared with that of International Prognostic Index (IPI), Prognostic Index for Peripheral T-cell lymphoma unspecified (PIT), and Korean Prognostic Index (KPI). Patients with higher GPS tended to have more adverse clinical characteristics, lower rates of complete remission (P < 0.001), inferior progression-free survival (PFS, P < 0.001), and inferior overall survival (OS, P < 0.001). Multivariate analysis demonstrated that high GPS, age > 60 years, and elevated LDH were independent adverse predictors of OS. GPS was found superior to IPI, PIT, and KPI in discriminating patients with different outcomes in low-risk groups (all P < 0.05). GPS is an independent predictor of survival outcomes in ENKL. Inflammatory response might play an important role in the progression of ENKL and survival of patients with ENKL.