This meta-analysis aims to evaluate the effect of n-3 polyunsaturated fatty acids (PUFAs) as a part of parenteral nutrition in patients undergoing liver surgery.Systematic review and meta-analysis.PubMed, the Cochrane Central Register of Controlled Trials, Springer link, Web of Science, China National Knowledge Infrastructure and VIP Database.We included randomised controlled trials (RCTs) and evaluated the outcomes of liver function, inflammatory reaction, the influence of certain markers of the immune system, and specific clinical indexes for patients undergoing liver surgery and receiving parenteral nutrition with n-3 PUFAs.The Cochrane Collaboration's tool was used to assess the risk of bias for each study. Findings were summarised in Grades of Recommendation, Assessment, Development and Evaluation evidence profiles and synthesised qualitatively.Eight RCTs, including 748 patients (trial: 374; control: 374), were included in the meta-analysis. Compared with patients in the control group, the patients in the n-3 PUFA group who underwent liver surgery had significantly lower aspartate aminotransferase (mean difference, MD -42.72 (95% CI -71.91 to -13.52); p=0.004), alanine aminotransferase (MD -38.90 (95% CI -65.44 to -12.37); p=0.004), white cell count (MD -0.93 (95% CI -1.60 to -0.26); p=0.007) and IL-6 (MD -11.37 (95% CI -14.62 to -8.13); p<0.00001) levels and a higher albumin level (MD 0.42 (95% CI 0.26 to 0.57); p<0.00001). They also had fewer infection complications (OR 0.44 (95% CI 0.28 to 0.68); p=0.0003) and a shorter duration of hospital stay (MD -2.17 (95% CI -3.04 to -1.3); p<0.00001) than the controls. However, there were no significant differences in terms of total bilirubin, TNF-α, IL-2, IgA, IgG, IgM and CD3, biliary leakage and mortality between the two groups.We found that n-3 PUFAs can benefit patients undergoing liver surgery by improving liver function and certain clinical indexes and decreasing related inflammation factors. However, there are limited RCTs on the application of n-3 PUFAs for patients undergoing liver surgery. Further evidence of the benefit of n-3 PUFAs in these patients warrants further exploration.© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.