Purpose: This study examines the relationship between Transport Management Systems (TMS) and the performance of Inter-Governmental Organizations (IGOs) in Nairobi City County. The research investigates how adopting TMS influences operational efficiency, cost reduction, and service delivery among IGOs. Methodology: A descriptive research design was employed, utilizing a census approach targeting 134 IGOs. Data was collected from supply chain managers using structured questionnaires, and descriptive and inferential statistical analyses were conducted. Pearson correlation and regression analysis were applied to determine the strength and significance of the relationship between TMS adoption and performance. Results: Findings revealed a significant positive correlation (r = 0.421, p < 0.001) between TMS adoption and IGO performance, indicating that organizations with well-integrated transport systems experience improved logistics efficiency and service delivery. Regression analysis further confirmed that TMS accounts for 53.7% of performance variations among IGOs. Theoretical Contribution: This study extends the application of Systems Theory by demonstrating the interdependence between transport management, logistics coordination, and organizational performance in an inter-governmental context. Practical Implications: IGOs in Nairobi City County can enhance operational efficiency by adopting advanced TMS solutions such as real-time tracking, route optimization, and automated reporting. Policymakers and stakeholders should also invest in infrastructure and regulatory frameworks that support effective transport management in IGOs.