Currently, platinum-based chemotherapy is the standard first-line treatment for advanced non-small cell lung cancer (NSCLC) that is not driven by identifiable genetic events, such as sensitizing mutations of epidermal growth factor receptor (EGFR) and translocations of anaplastic lymphoma kinase (ALK). Immune checkpoint inhibitors, which unleash a patient's own T cells to attack tumors, are revolutionizing the treatment paradigm of lung cancer. Anti-programmed death 1 (anti-PD-1) antibodies, pembrolizumab and nivolumab, and anti-programmed death ligand 1 (anti-PD-L1) antibody atezolizumab have shown a significantly longer survival and manageable safety profile, being approved as first or second-line treatment options in patients with advanced non-small cell lung cancer. Only the pembrolizumab approval is limited to the PD-L1-positive NSCLC; both nivolumab and atezolizumab can be currently used irrespective of tumor PD-L1 expression. Biomarkers for the response to PD-1/PD-LI checkpoint inhibitors beyond PD-L1 expression levels are being investigated in order to select patients who are most likely to benefit from antibodies targeting the PD-1 axis.