In recent years, the development of targeted therapies for tumors with KRAS mutations has progressed rapidly, rendering the notion of KRAS as "undruggable" outdated. However, targeted therapies for KRAS mutations still face numerous challenges, including resistance, efficacy concerns, toxicity issues, and hurdles in drug development. Exploring alternative treatment modalities is thus essential. Extensive research has demonstrated that KRAS mutations significantly influence the immune microenvironment, presenting both challenges and opportunities for immunotherapy. Interestingly, it has been observed that different KRAS mutations and co-mutation subtypes exhibit significant variations in their immunological microenvironments, which undoubtedly impact immunotherapy choices. Here, we review the history of KRAS-targeted therapy, highlighting existing challenges, and summarize changes in the immune microenvironment of KRAS-mutated cancers and their potential therapeutic targets. We compare differences in the immune microenvironment across various mutation types and co-mutation subtypes, and offer perspectives on future research directions.