Malnutrition is common in both adult and pediatric patients undergoing treatment for cancer. Patients commonly attribute difficulties maintaining food intake to an altered taste developed during treatment. This review summarizes what is known about taste and smell dysfunction in patients with undergoing chemotherapy as their main treatment modality. Self-reported taste and smell alterations are prevalent in upwards of 86% of cancer patients. There is some evidence for decreased taste sensitivity in cancer patients when assessed using common gustatory tests. In some patients, taste and smell alterations may continue well after their cancer treatment has been completed. Such disorders can increase distress, reduce appetite and contribute towards poor nutritional status in cancer patients. There remain no effective interventions for improving the appetite or nutritional intake of patients with cancer experiencing taste and smell changes. There is a lack of consistency in assessment methodologies for measuring taste and smell changes in cancer patients and we therefore recommend that future work use well-established methods. Research should also take into account the role of food hedonics, food flavor and texture in assessing the association between taste dysfunction, poor oral intake and malnutrition in cancer patients. Both adult and child cancer patients should be counselled on the potential impact taste and smell dysfunction can have on their appetite and oral intake.