Approximately 20% of lung adenocarcinomas harbor activating mutations at KRAS , an oncogene with the ability to alter the tumor immune microenvironment. In this retrospective study, we examined 103 patients with KRAS -mutant lung adenocarcinoma who were treated with immunotherapy-based regimens and we evaluated the clinical outcomes according to PD-L1 expression and the type of KRAS mutation. Among all patients included, 47% carried KRAS G12C mutation whereas 53% harbored KRAS non-G12C mutations. PD-L1 status was available for 77% of cases, with higher expression among KRAS G12C tumors (p = 0.01). Better overall survival and progression-free survival were observed in high PD-L1 expression tumors, regardless of KRAS mutation type. The heterogeneous nature of KRAS-mutant tumors and the presence of other co-mutations may contribute to different outcomes to immunotherapy-based strategies.