AJCC TNM stage and WHO grade (G) are two widely used staging systems to guide clinical management for pancreatic neuroendocrine neoplasms (panNENs), based on clinical staging and pathological grading information, respectively. We proposed to integrate TNM stage and G grade into one staging system (TNMG) and to evaluate its clinical application as a prognostic indicator for panNENs. Accordingly, 5254 patients diagnosed with panNENs were used to evaluate and to validate the applicability of TNMG to panNENs. The predictive accuracy of TNMG system was compared with that of each separate staging/grading system. We found that TNM stage and G grade were independent risk factors for survival in both the Surveillance, Epidemiology, and End Result (SEER) and multicenter series. The interaction effect between TNM stage and G grade was significant. Twelve subgroups combining the TNM stage and G grade were proposed in the TNMG stage, which were classified into five stages TNMG. According to the TNMG staging classification in the SEER series, the estimated median survival for stages I, II, III, IV, and V were 203, 174, 112, 61, and 8 months, respectively. The predictive accuracy of TNMG stage was higher than that of TNM stage and G grade used independently. The TNMG stage classification was more accurate in predicting panNEN patient's prognosis than either the TNM stage or G grade.