This study examines the effect of Treasury Single Account (TSA) implementation on revenue leakage in Nigerian public institutions, covering the period 2015 to 2024. The study is motivated by the persistent problem of unremitted internally generated revenue, proliferation of unauthorised bank accounts and systemic revenue diversion that characterised public financial management in Nigeria prior to and during TSA rollout. The specific objectives are to examine the effect of TSA compliance on revenue leakage reduction, to determine the effect of revenue consolidation on revenue leakage reduction, and to assess the effect of financial accountability on revenue leakage reduction in Nigerian public institutions. An ex-post facto research design was adopted, utilising secondary data sourced from the Central Bank of Nigeria (CBN) Annual Reports, the Office of the Accountant-General of the Federation (OAGF) Financial Statements, and the Auditor-General for the Federation (AuGF) Annual Reports. Ordinary Least Square (OLS) regression analysis was employed alongside descriptive statistics, normality test, Pearson correlation, Variance Inflation Factor (VIF), and heteroscedasticity diagnostics. Findings reveal that TSA compliance, revenue consolidation, and financial accountability each exert significant negative effects on revenue leakage, confirming that TSA implementation substantially reduces revenue leakage in Nigerian public institutions. It is recommended that the scope of TSA implementation be extended to all tiers of government and that institutional oversight mechanisms be strengthened to sustain the revenue-protection gains achieved through the TSA framework.