Purpose One-anastomosis gastric bypass (OAGB) has become increasingly popular due to shorter operative times and lower perioperative complication rates compared to Roux-en-Y gastric bypass (RYGB). However, OAGB is associated with short- and long-term complications, including reports of liver dysfunction that may result in death or liver transplantation. Methods A systematic review and meta-analysis were performed following PRISMA guidelines. MEDLINE, EMBASE, and PubMed were searched to identify studies reporting liver dysfunction post-OAGB. Two independent reviewers conducted data extraction and quality assessment. Statistical analyses included pooled prevalence estimates, subgroup analyses (biliopancreatic limb length, geographic regions), sensitivity analysis, and publication bias assessment using Egger’s test. Results Of 3,223 articles screened, 7 studies met inclusion criteria, representing 2,969 patients, with 91 developing liver dysfunction post-OAGB. The pooled prevalence was 1.2% (95% CI: 0.3–2.1%), with significant heterogeneity (I² = 88.5%, p < 0.001). Subgroup analyses, including biliopancreatic limb length, revealed no significant associations with liver dysfunction prevalence. Heterogeneity contributors were not identified. Sensitivity analyses confirmed the robustness of findings, and no publication bias was detected. Conclusion The prevalence of liver dysfunction post OAGB is low but clinically significant, warranting intense postoperative care and regular liver function monitoring. The lack of extensive data on this topic is a limitation, but as the first study to summarise current evidence this study provides a foundation for future research.