PURPOSE: Resistance to immune checkpoint inhibition (ICI) in advanced non-small-cell lung cancer (NSCLC) represents a major unmet need. Combining ICI with vascular endothelial growth factor (VEGF)/VEGF receptor inhibition has yielded promising results in multiple tumor types. METHODS: In this randomized phase II Lung-MAP nonmatch substudy (S1800A), patients ineligible for a biomarker-matched substudy with NSCLC previously treated with ICI and platinum-based chemotherapy and progressive disease at least 84 days after initiation of ICI were randomly assigned to receive ramucirumab plus pembrolizumab (RP) or investigator's choice standard of care (SOC: docetaxel/ramucirumab, docetaxel, gemcitabine, and pemetrexed). With a goal of 130 eligible patients, the primary objective was to compare overall survival (OS) using a one-sided 10% level using the better of a standard log-rank (SLR) and weighted log-rank (WLR; G[rho = 0, gamma = 1]) test. Secondary end points included objective response, duration of response, investigator-assessed progression-free survival, and toxicity. RESULTS: Of 166 patients enrolled, 136 were eligible (69 RP; 67 SOC). OS was significantly improved with RP (hazard ratio [80% CI]: 0.69 [0.51 to 0.92]; SLR one-sided = .05; WLR one-sided = .15). The median (80% CI) OS was 14.5 (13.9 to 16.1) months for RP and 11.6 (9.9 to 13.0) months for SOC. OS benefit for RP was seen in most subgroups. Investigator-assessed progression-free survival (hazard ratio [80% CI]: 0.86 [0.66 to 1.14]; one-sided SLR, = .25 and .14 for WLR) and response rates (22% RP 28% SOC, one-sided = .19) were similar between arms. Grade ≥ 3 treatment-related adverse events occurred in 42% of patients in the RP group and 60% on SOC. CONCLUSION: This randomized phase II trial demonstrated significantly improved OS with RP compared with SOC in patients with advanced NSCLC previously treated with ICI and chemotherapy. The safety was consistent with known toxicities of both drugs. These data warrant further evaluation.