The evaluation of quality of life (QoL) assesses patients' well-being by taking into account physical, psychological and social conditions. Cancer and its treatment result in severe biochemical and physiological alterations associated with a deterioration of QoL. These metabolic changes lead to decreased food intake and promote wasting. Cancer-related malnutrition can evolve to cancer cachexia due to complex interactions between pro-inflammatory cytokines and host metabolism. Beside and beyond the physical and the metabolic effects of cancer, patients often suffer as well from psychological distress, including depression. Depending on the type of cancer treatment (either curative or palliative) and on patients' clinical conditions and nutritional status, adequate and patient-tailored nutritional intervention should be prescribed (diet counselling, oral supplementation, enteral or total parenteral nutrition). Such an approach, which should be started as early as possible, can reduce or even reverse their poor nutritional status, improve their performance status and consequently their QoL. Nutritional intervention accompanying curative treatment has an additional and specific role, which is to increase the tolerance and response to the oncology treatment, decrease the rate of complications and possibly reduce morbidity by optimizing the balance between energy expenditure and food intake. In palliative care, nutritional support aims at improving patient's QoL by controlling symptoms such as nausea, vomiting and pain related to food intake and postponing loss of autonomy. The literature review supports that nutritional care should be integrated into the global oncology care because of its significant contribution to QoL. Furthermore, the assessment of QoL should be part of the evaluation of any nutritional support to optimize its adequacy to the patient's needs and expectations.