Malnutrition and muscle wasting are common and serious concerns for patients with cancer, yet nutritional risk is often under-recognised and under-treated by clinicians and care teams. This review highlights that early and proactive nutritional screening, assessment, and individualised intervention are essential parts of oncology care. Evidence and guidelines support integrating nutrition counseling and, when needed, oral nutritional supplements to improve body composition, treatment tolerance, quality of life, and survival. A multidisciplinary approach, with nutrition as a central component, is recommended to optimise outcomes for cancer patients.