Objectives: To conduct a comprehensive evidence synthesis to verify the available literature on the effects of exercise intervention on muscle mass, muscle strength, and physical function in older adults with muscle wasting. Methods: Systematic literature searches of the PubMed/Medline, CINAHL, EMBASE, Cochrane Library, and Airiti Library databases were performed for exercise-related randomized controlled trials among adults aged 60 years and above with muscle wasting disease, published from 2010 to April 30, 2021. The search included the keywords and synonyms: "older," "sarcopenia," "cachexia," "muscle wasting," "exercise'. Results: The systematic review included 34 studies: 25 on patients with sarcopenia and 9 on patients with cachexia. Sarcopenia and cachexia were analyzed as separate subgroups. The effects of exercise in the sarcopenia group showed significant improvement in the following parameters: body composition (appendicular skeletal muscle [ASM] [standardized mean difference, SMD 0.38, P = 0.05] and ASM/height2 [SMD 0.14, P = 0.02]), muscle strength (grip strength [SMD 1.73, P < 0.0001]), and physical performance (gait speed [SMD 0.14, P < 0.00001] and the timed up and go test [SMD -1.20, P < 0.00001]). Similarly, in the cachexia group, exercise intervention showed improvement in the body composition (ASM [SMD 3.38, P = 0.001]) and physical performance (400 m walk [SMD -36.00, P = 0.02]). Conclusions: Exercise intervention has significant benefits in older adults with muscle wasting diseases. More well-designed large-sample-sized studies with long-term follow-ups are warranted to verify the benefits of exercise intervention in this population.