This study investigates the impact of developmental Human Resource (HR) practices—specifically, employee training (ET), career development (CD), and performance appraisal (PA)—on project performance (PP), with a particular focus on employee engagement (EE) as a mediating variable. Developmental HR strategies aim to strengthen employees' skills, motivation, and overall contributions to organizational success, particularly within project management contexts where deadlines, costs, and quality are critical factors. Adopting a quantitative methodology, the research analysed data from 199 participants using validated measurement tools. The findings reveal that ET and PA significantly enhance employee engagement, which in turn positively affects project performance. Although CD does not exert a direct significant effect on EE, it contributes to improved project outcomes when mediated by EE. These results underscore the importance of fostering employee engagement as a crucial link between HR practices and project performance. The study provides strategic insights for organizations on leveraging developmental HR practices to achieve project success. However, its cross-sectional design and reliance on self-reported data present limitations. Future research should explore longitudinal approaches and consider additional mediators, such as organizational culture or leadership, to deepen the understanding of HR's impact on project performance.