This phase 2, single-arm, multicenter clinical trial plans to enroll 152 patients with newly-diagnosed, pathologically-proven, untreated locoregionally advanced nasopharyngeal carcinoma (LANPC) at high-risk of distant metastasis (T4N1M0 or T1-4N2-3M0, according to American Joint Committee on Cancer [AJCC]/Union for International Cancer Control [UICC] 8th edition clinical staging system). Patients will receive 3 cycles of induction chemotherapy (IC; gemcitabine-cisplatin regimen) followed by intensity-modulated radiotherapy (IMRT) alone. Nivolumab injection OPDIVO® will start on day 1 of the first cycle IC and continue every 3 weeks for 6 cycles till the end of IMRT, involving the whole-course of IC + IMRT alone. The first and last 3 cycles of nivolumab are administrated concurrently with IC and IMRT, respectively. After the completion of IMRT, adjuvant nivolumab will begin every 4 weeks for 6 cycles.