The purpose of this study was to investigate the role of early radiotherapy in patients with localized-stage nasal-type natural killer (NK)/T cell lymphoma treated with L-asparaginase-containing chemotherapy. Sixty-four patients with stage I-II nasal-type NK/T cell lymphoma were enrolled in this study. All patients received an L-asparaginase-containing regimen. Thirty-four patients received late radiotherapy (RT), which was defined as receiving 6 cycles of prior chemotherapy (CT) followed by RT, and 30 patients received early RT, which was defined as receiving no more than 3 cycles of CT followed by early RT. With a median follow-up of 35 months (range, 12-49 months), 19 patients (29.7 %) died from lymphoma-related causes, and 22 patients (34.4 %) developed local and/or distant relapse. The 3-year overall survival (OS) and progression-free survival (PFS) were 84.2 and 74.3 % for early RT and 57.6 and 55.9 % for late RT, respectively, and these differences were significant (OS, p = 0.027; PFS, p = 0.034). After 2 cycles of initial CT, 58 patients achieved treatment response (complete response and partial response). For the 58 patients, there were still significant differences for 3-year OS and PFS when early RT was compared with late RT (3-year OS 94.4 vs. 58 %, P = 0.005; 3-year PFS 82.9 vs. 56.3 %, P = 0.01). Early RT has an essential role in improving survival for localized-stage nasal-type NK/T cell lymphoma (TCL) patients even when used in combination with L-asparaginase-containing CT. Prospective, randomized studies should to be performed to confirm these results.