Sarcopenia is considered as a clinical syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength, and impaired muscular function. Sarcopenia has recently emerged as a new condition and more recently research has focused on cancer patients who appear to be especially exposed to this risk. Sarcopenia has received great attention by clinicians in the oncology field. Sarcopenia is the major feature of cancer cachexia, and is associated with reduced quality of life and survival. There are several reasons for muscle mass depletion in cancer patients, such as higher energy expenditure, anorexia, inflammation and unbalanced cancer metabolism. To explore the relationship between sarcopenia and cancer chemotherapy, purpose of this review is to define the diagnosis of sarcopenia in cancer patients, the prevalence of sarcopenia in cancer patients, its role in leading to chemotherapy toxicity and its effect on the prognosis in cancer patients. Finally, the review also aims to describe the current approaches to restore the muscle mass and the effects on the therapy in cancer patients.  Recent researches has allowed the oncologist to evaluate the muscle mass and to collect many data on the prevalence of sarcopenia and its clinical consequences. 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 cancer patient and improve the outcome of the cancer patients.