This paper seeks to examine project planning as a crucial instrument of project management practices and its effect on the success of the project in the public sector in Nigeria using selected government institutions in Plateau state. The study was inspired by the desire to investigate the level of contribution of project planning to successful project delivery in public institutions. A quantitative survey research design was adopted for the study. The population of the study comprised 100 staff of the procurement and works departments of selected tertiary institutions in Plateau state. This small population size was due to the focus on specific departments within a limited number of institutions; however, it may limit the generalizability of findings. Future studies should consider expanding the scope to include more institutions and departments. The empirical results show that project planning has a positive and significant effect on successful project delivery in the selected public institutions (β = 0.442, t = 10.517, p < 0.001). Multicollinearity diagnostics (e.g., VIF) should be reported to ensure the robustness of the regression estimates. In addition, focus needs to be given not just to the development of project plans, but also their implementation, tracking and regular review throughout the project life cycle to improve projects' results.