Low serum albumin is predictive of poor survival in nasopharyngeal carcinoma (NPC). We evaluated the ability of the pretreatment albumin/globulin ratio (AGR) to predict long-term mortality in patients with NPC. This retrospective study examined an unselected cohort of 694 patients with NPC who had documented pretreatment total serum protein and serum albumin levels (ALB). AGR was calculated as AGR = ALB/(total serum protein--ALB). Survival analysis was used to evaluate the predictive value of AGR. Multivariate analysis demonstrated that a low pretreatment serum AGR (<1.4) was an independent predictor of poor OS (P  = 0.029) and DMFS (P  = 0.033). A low AGR was significantly associated with advanced stage disease (P<0.001), high white blood cell count (P  = 0.033), high neutrophil count (P  = 0.047), high total serum protein (P<0.001) and low ALB (P<0.001). The pretreatment AGR may represent a simple, potentially useful predictive biomarker for evaluating the long-term prognosis of patients with undifferentiated NPC.