There have been no reviews describing the efficacy of the combination of both rehabilitation and nutritional treatments. This systematic review aimed to assess the effects of nutritional therapy on patients with an acute and critical illness undergoing rehabilitation. Online searches using PubMed (MEDLINE), Cochrane Central Register of Controlled Trials, EMBASE (ELSEVIER), and Ichu-shi Web databases identified 986 articles, and 16 additional articles were found through other sources. Each trial assessed for the risk of bias using the Cochrane Collaboration's tool, and the quality of the body of evidence with The Grading of Recommendations Assessment, Development and Evaluation approach. Two randomized controlled trials were included in this review. Jones et al reported that with an enhanced rehabilitation program, there was no effect of nutritional intervention on quality of life (standardized mean difference [SMD] 0.55, 95% confidence intervals [CI] -0.05 to 1.15; P = 0.12). However, Hegerova et al reported positive effects of physical therapy and oral supplements on muscle mass (0.65; 95% CI, 0.36 to 0.93; P < 0.00001) and activities of daily living (SMD 0.28, 95% CI 0.00 to 0.56; P = 0.05). Strengthened nutritional intervention with enhanced rehabilitation treatment for patients with acute and critical illness may possibly be effective for increasing muscle mass, as well as for improving activities of daily living within a short period after discharge.