Background: Acute kidney injury (AKI) is associated with increased morbidity and mortality and may present as oliguria in the post-operative phase. Diuretics, including furosemide, are commonly used in post-operative patients. Accordingly, we aimed to assess the balance between benefits and harms of furosemide post-operatively in adult surgical patients. Methods: We conducted a systematic review with meta-analysis according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statements, the Cochrane Handbook and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology. We included randomised clinical trials (RCTs) comparing post-operative treatment with furosemide vs no furosemide in adult surgical patients. Risk ratios (RR) with 95% confidence intervals (CI) were estimated by conventional meta-analysis and trial sequential analysis (TSA). Results: Two thousand five hundred and sixty seven records were identified and four trials with 325 patients in total were included. All were adjudicated as having overall high risk of bias. We observed no statistically significant difference between furosemide- vs no furosemide-treated patients in any of the predefined outcome measures, including AKI (RR 1.07, 95% CI 0.43-2.65), all-cause mortality (RR 1.73, 95% CI 0.62-4.80, use of vasopressors post-operatively (RR 1.04, 95% CI 0.74-1.44) or need for renal replacement therapy (RR 3.87, 95% CI 0.44-33.99). TSA highlighted sparse data, and the overall quality of evidence was very low. Conclusion: In this systematic review, we found that the quantity and quality of evidence for using furosemide post-operatively in adult surgical patients were very low with no firm evidence for benefit or harm.