Fleet management is one of the most critical yet underexplored strategic functions in transport organizations operating in resource-constrained environments. This study examined the effect of fleet management practices, specifically maintenance management, fuel management, and driver management, on the organizational performance of National Transport PLC, a major freight transport company in Ethiopia. The study was motivated by persistent operational inefficiencies in the Ethiopian transport sector, including frequent vehicle breakdowns, rising fuel costs, unsafe driving practices, and limited adoption of modern fleet technologies. The study was guided by Resource-Based View (RBV) Theory, Systems Theory, Reliability-Centered Maintenance (RCM) Theory, and Human Capital Theory, which provided the theoretical foundation for examining the relationship between fleet management practices and organizational performance. A quantitative research approach with an explanatory research design was employed. Data were collected from 223 respondents out of 229 distributed questionnaires, achieving a response rate of 97.4%. Multiple linear regression analysis was used to examine the relationships among the study variables. The findings revealed that maintenance management and fuel management practices had a statistically significant and positive effect on organizational performance, while driver management showed a positive but statistically non-significant effect. Maintenance management emerged as the strongest predictor, followed by fuel management and driver management. Together, the three practices explained 76.6% of the variance in organizational performance. The study concludes that treating fleet management as an integrated system rather than isolated activities substantially improves vehicle availability, cost efficiency, safety, and service reliability. The study recommends that transport companies in Ethiopia and similar developing contexts invest in coordinated maintenance systems, effective fuel management practices, and continuous driver development programs to enhance organizational performance and operational sustainability.