This study was launched to determine the prognostic significance of local tumor invasiveness (LTI) in 114 patients diagnosed with stage I(E)/II(E) extranodal natural killer (NK)/T-cell lymphoma, nasal type (NTCL). LTI was defined as bony invasion or destruction or tumor invasion of the skin. Complete remission (CR), overall survival (OS), and disease-free survival (DFS) were compared between each group according to LTI, Ann Arbor stage, and International Prognostic Index (IPI). LTI was observed in 23 patients. Using multivariate analysis, factors associated with low probability of CR were the presence of LTI (P < .001), the presence of B symptoms (P = .003), and single-modality chemotherapy (P = .045). The presence of LTI (relative risk [RR] = 8.4, 95% confidence interval [CI] 3.9-17.9; P < .001) and high IPI score (RR = 2.8, 95% CI 1.2-6.8; P = .019) were also predictive of OS. The presence of LTI (RR = 7.3, 95% CI 3.2-16.5; P < .001) was an independently significant factor for reduced DFS. Ann Arbor staging system did not predict CR, OS, or DFS but IPI did have predictive power with regard to survival outcome. LTI is the most important prognostic factor in predicting low probability of CR and reduced OS and DFS in nasal stage I(E)/II(E) NTCL.