Sarcopenia has recently emerged as a new condition that, independently from malnutrition, may adversely affect the prognosis of cancer patients. Purpose of this narrative review is to define the prevalence of sarcopenia in different primaries, its role in leading to chemotherapy toxicity and decreased compliance with the oncological therapy and the effect of some drugs on the onset of sarcopenia. Finally, the review aims to describe the current approaches to restore the muscle mass through nutrition, exercise and anti-inflammatory agents or multimodal programmes with a special emphasis on the results of randomized controlled trials. The examination of the computed tomography scan at the level of the third lumbar vertebra-a common procedure for staging many tumours-has allowed the oncologist to evaluate the muscle mass and to collect many retrospective data on the prevalence of sarcopenia and its clinical consequences. Sarcopenia is a condition affecting a high percentage of patients with a range depending on type of primary tumour and stage of disease. It is noteworthy that patients may be sarcopenic even if their nutritional status is apparently maintained or they are obese. Sarcopenic patients exhibited higher chemotherapy toxicity and poorer compliance with oncological treatments. Furthermore, several antineoplastic drugs appeared to worsen the sarcopenic status. Therapeutic approaches are several and this review will focus on those validated by randomized controlled trials. They include the use of ω-3-enriched oral nutritional supplements and orexigenic agents, the administration of adequate high-protein regimens delivered enterally or parenterally, and programmes of physical exercise. Better results are expected combining different procedures in a multimodal approach. In conclusion, there are several premises to prevent/treat sarcopenia. The oncologist should coordinate this multimodal approach by selecting priorities and sequences of treatments and then involving a nutrition health care professional or a physical therapist depending on the condition of the single patient.