Cancer remains a leading global cause of morbidity and mortality. While conventional therapies such as chemotherapy and radiation are essential, growing evidence supports the adjunctive use of nutraceuticals-bioactive compounds from natural food sources-with anticancer potential. To synthesize current evidence on the mechanisms, therapeutic roles, and clinical challenges of nutraceuticals in cancer chemotherapy. A narrative review was conducted by searching literature from 2015 to 2024 across PubMed, Scopus, and Web of Science. Studies were included based on relevance to cancer patients, nutraceutical interventions, and reported therapeutic or supportive outcomes. No formal meta-analysis was performed; findings were thematically grouped and summarized. Nutraceuticals such as curcumin, resveratrol, flavonoids, and vitamins D and E exert antioxidant, anti-inflammatory, pro-apoptotic, and immune-modulatory effects. Many demonstrate synergy with chemotherapy, enhancing efficacy and reducing toxicity. Probiotics and omega-3 fatty acids, in particular, show promise in alleviating chemotherapy-induced side effects. However, clinical utility is limited by inconsistent trial results, variable dosing, low bioavailability, and lack of regulatory oversight. Some supplements may interfere with standard therapies or pose safety concerns if used indiscriminately. Nutraceuticals offer promising adjunctive benefits in cancer care, but their integration requires cautious, evidence-based application. Standardized formulations, better clinical trial designs, and regulatory clarity are needed to ensure their safe and effective use in oncology.