Bioelectrical impedance analysis is non-invasive, validated method to assess body composition and nutritional status, which offers an efficacious way to track changes in body composition over time. Cancer patients have different rates of malnutrition due to the type, location, stage, and treatment route of the tumor. Malnutrition is commonly reported in cancer patients and can increase mortality and treatment complications, and can reduce treatment effectiveness and quality of life. Cancer patients are usually at risk of developing cachexia, which is associated with progressive weight loss, loss of muscle and fat tissue, impaired immune function, and metabolic disturbances caused by a variable combination of reduced food intake, systemic inflammation and abnormal metabolism. The bioelectrical impedance analysis method can qualitatively and quantitatively analyze the composition of different tissues in the body and accurately reflect the changes of the components of the body. It is a good tool for evaluating the nutritional status of cancer patients. Studies indicate that the use of bioelectrical impedance analysis and phase angle measures can benefit in the clinical management of cancer patients in multiple ways: in the prevention, diagnosis and prognosis. The phase angle and fatfree mass obtained by bioelectrical impedance analysis has been used as a predictor of nutritional status and survival rate in cancer patients. This systematic review sought to summarise current literature surrounding body composition assessment in cancer patients to provide a basis for clinical nutrition monitoring and nutritional support.