This study examined the relationship between leadership styles and employee productivity in the University of Port Harcourt, Nigeria. Specifically, it focused on how transformational and transactional leadership styles influence two key indicators of employee productivity: service timeliness and service quality. A cross-sectional survey design was employed, with 196 valid responses collected from non-academic staff across various administrative units. The data was analyzed using Partial Least Squares Structural Equation Modeling (PLS-SEM) via SmartPLS 4.0. Findings revealed that both leadership styles had significant positive effects on employee productivity dimensions, with transformational leadership demonstrating stronger effects. The study concludes that effective leadership is critical for enhancing service performance in tertiary institutions and recommends targeted leadership development programs that emphasize both transformational and transactional elements to achieve a balanced improvement in timeliness and quality of service.