Amino acid (AA) infusion is sometimes selected to avoid hypothermia during general anesthesia. However, the widespread clinical use of AA infusion therapy has not been established. This study aimed to clarify the evidence that AA infusion can increase patient body temperature and improve clinical outcomes using the Grading of Recommendations Assessment, Development, and Evaluation system. We searched MEDLINE (PubMed), Cochrane Central Register of Controlled Trials, and Igaku Chuo Zasshi (Japana Centra Revuo Medicina) in November 2015. Studies were reviewed by 2 independent assessors to identify randomized controlled trials (RCTs) involving AA infusion compared with placebos during surgery under general or combined general/epidural anesthesia. Study quality was assessed using the Grading of Recommendations Assessment, Development, and Evaluation system and the Cochrane methodology. The primary outcome was difference in body temperature before and after perioperative AA infusion. Shivering frequency, blood loss volume, postoperative intubation time, and hospitalization period were also assessed as clinical outcomes. We analyzed the outcome data using a random effect model. From 298 screened titles, 14 RCTs met our inclusion criteria, including 626 patients (327 in AA and 299 in placebo groups). In 626 participants from 14 RCTs, AA infusion increased body temperature by a mean difference (MD) of 0.46°C (95% confidence interval [CI], 0.31–0.62, low-quality evidence). Regarding other outcomes, AA infusion decreased shivering frequency by a risk ratio of 0.34 (95% CI, 0.12–0.94; 7 RCTs, 248 participants, very low-quality evidence), shortened postoperative intubation time by MD of −125 minutes (95% CI, −210 to −38.8; 2 RCTs, 158 participants, moderate-quality evidence), and shortened the hospitalization period by MD of −1.81 days (95% CI, −2.07 to −1.55; 3 RCTs, 230 participants, low-quality evidence) compared with placebo. There was no significant difference in the volume of blood loss between the 2 groups (standardized MD, −0.20, 95% CI, −0.44 to 0.04; low-quality evidence). There was no publication bias. AA infusion in the perioperative period increased patient body temperature and improved clinical outcomes compared with placebo. However, the evidence to support the use of AA infusion is limited, and further large-scale RCTs are required.