Emerging evidence on the role of the antitumor activity of the immune system has generated great interest in immunotherapy even for tumors that were historically considered as nonimmunogenic. Immunotherapy is emerging as a major modality in non–small cell lung cancer (NSCLC) treatment focusing on vaccine approaches to elicit specific immune responses and development of inhibitors of the molecular mediators of cancer-induced immunosuppression (immune checkpoints) to boost antitumor immune responses. Amplification of the host response against evolving tumors through vaccination is being investigated in ongoing clinical trials with tumor cell vaccines; however, the clinical efficacy of these agents has been limited. Blocking inhibitory pathways such as the CTL antigen 4 (CTLA-4) and programmed cell death 1 (PD-1) checkpoint pathways with mAbs has generated antitumor immune responses that are transforming cancer therapeutics. PD-1 and programmed cell death ligand 1 (PD-L1) antibodies have shown durable responses in NSCLC, with a favorable safety profile and manageable side effects. The activity of immune checkpoint inhibitors is currently been assessed in treatment-naïve patients with PD-L1–positive advanced NSCLC. Combinatorial approaches with other immune checkpoint inhibitors, chemotherapy, or targeted agents are being explored in ongoing clinical trials, and may improve outcome in NSCLC. Clin Cancer Res; 21(5); 976–84. ©2015 AACR.