This study presents a comprehensive systematic review and meta-analysis of randomized controlled trials (RCTs) on Chlorella vulgaris (C. vulgaris) supplementation and liver function biomarkers. Pertinent studies were identified using Scopus, ISI Web of Science, PubMed, and Cochrane library databases up to August 2020. Mean differences were pooled using a random-effects model. Pooling 7 RCTs together showed that C. vulgaris supplementation led to a significant reduction of serum aspartate aminotransferase (AST) levels (weighted mean difference WMD, -9.15 U/L; 95% confidence interval CI, -16.09, -2.21), but not alanine aminotransferase (ALT) or alkaline phosphatase (ALP) levels compared to the placebo consumption. Subgroup-analysis indicated that C. vulgaris supplementation had more effect on AST decreasing among non-alcoholic fatty liver disease patients (WMD, -16.42 U/L; 95% CI, -29.75, -3.09) than others. Furthermore, subgroup analysis based on kind of supplementation showed that C. vulgaris supplementation significantly decreased ALT levels (WMD, -4.65 U/L; 95% CI, -8.88, -0.42) compared with the placebo, but not metformin consumption. It seems that C. vulgaris supplementation mainly affects AST levels rather than ALT and ALP levels, however, as mentioned the effect of C. vulgaris on those enzymes might be context-dependent. Therefore, further investigations with a large number of patients as well as on different disorders are necessary and can provide more definitive evidence.