Chemotherapy remains a cornerstone in cancer management; however, its non-selective cytotoxic effects frequently result in significant oral mucosal complications that adversely affect patient wellbeing and treatment outcomes. The oral mucosa is particularly susceptible to injury because of its rapid epithelial turnover, rich vascularity, and constant exposure to mechanical and microbial insults. Chemotherapy-induced oral changes commonly include oral mucositis, xerostomia, opportunistic infections, dysgeusia, ulcerative lesions, mucosal pigmentation, and bleeding manifestations. Among these, oral mucositis is the most common and debilitating complication, often leading to pain, dysphagia, impaired nutrition, reduced quality of life, and interruption of cancer therapy. The pathogenesis involves direct epithelial toxicity, oxidative stress, inflammatory cytokine activation, and breakdown of the mucosal barrier, predisposing patients to secondary infections and delayed healing. Early diagnosis, preventive oral care, and multidisciplinary management are essential for minimizing morbidity and improving therapeutic outcomes. This review summarizes the pathogenesis, clinical manifestations, diagnosis, prevention, and management of chemotherapy-induced oral mucosal changes.