Advanced-stage extranodal natural killer/T-cell lymphoma (ENKTL) is a highly heterogeneous disease with very poor prognosis. All commonly utilized prognostic models incorporated both early-stage and advanced-stage patients in the modeling process. This study aim to design a prognostic model specifically for advanced-stage ENKTL, providing risk stratification in affected patients. We analyzed 291 patients with stage III/IV ENKTL receiving asparaginase-based chemotherapy from 8 institutions to develop a new prognostic model and validate it in an independent cohort consisted of 221 patients from 4 additional hospitals. The prognostic model included three independent variables based on a multivariate analysis for overall survival (OS): age, bone marrow invasiveness and visceral organ involvement. We identified three different risk groups: group 1, no adverse factors; group 2, one factor; and group 3, two or three factors, which were associated with 5-year OS rates of 66.0%, 32.3%, and 20.0%, respectively (P < 0.001). The prognostic index of natural killer lymphoma (PINK) and nomogram-revised risk index (NRI) were unsatisfactory for stratifying these patients. These results were validated and confirmed in an independent cohort. This newly proposed model can be used to guide risk-adapted treatment for advanced stage ENKTL.