Skeletal muscle’s metabolic and mechanical functions make it critical for maintaining human health, physical function, and quality of life in adults. The impact of skeletal muscle mass and the metabolic quality of muscle tissue becomes even more critical with advancing age and in patients with chronic diseases. To this end, cachexia is the involuntary loss of body weight, including muscle and fat loss, accompanying an underlying disease or condition. Cancer-induced cachexia occurs across many types of cancer and contributes to increased patient mortality, morbidity, and treatment toxicities, negatively impacting survival. Furthermore, there are currently no approved pharmacological treatments and limited evidence-based therapeutic options to prevent muscle loss or promote muscle recovery in cancer patients. While the systemic effects of cancer and subsequent treatment continue to be examined as drivers of overall wasting, the impact of skeletal muscle mass and metabolic quality in the cancer patient remains a critical area of investigation. A vital knowledge gap exists in understanding how maintaining muscle function and metabolic properties improves cancer patients’ survival. The chapter explores the current understanding of how cancer and subsequent treatment impact skeletal muscle mass, function, and metabolic quality. To this end, the current understanding of systemic mediators and metabolic crosstalk between tissues that promote cancer-induced wasting is explored. Additional factors related to sex, physical activity level, chemotherapy-specific effects, and cancer heterogeneity are discussed concerning their impact on cancer-induced muscle wasting.