Oral mucosal toxicities are serious complications associated with conventional cytotoxic radiation and drug-based cancer regimens, and novel treatments such as immunotherapy and targeted agents. These toxicities, including oral mucositis, mammalian target of rapamycin inhibitor-associated stomatitis, oral immune-related adverse events, oral lichenoid lesions secondary to rituximab or imatinib, and geographic tongue associated with bevacizumab, sorafenib, sunitinib, or axitinib, can lead to significant morbidity, potentially compromising cancer treatment outcomes by necessitating treatment dose reductions, interruptions, or discontinuation. This review discusses the epidemiology, clinical presentation, pathobiology, and current management strategies for these oral mucosal toxicities. With the evolution of novel cancer therapies, including immunotherapy and targeted agents, oral mucosal toxicities have become more prevalent, presenting significant management challenges. Advances in understanding the pathobiology of these complications have led to the development of promising therapeutic strategies. However, variability in patient responses underscores the need for precision medicine approaches that tailor treatments to individual molecular and immunological profiles. While the standardization of clinical trials has improved the comparability of interventions, therapies must be rigorously tested to ensure they do not interfere with the oncologic efficacy of cancer treatments. Ongoing research is essential to refine preventive and therapeutic approaches.