Objective: Grounding on social learning theory (SLT), this study examines the effect of public leadership on project management effectiveness (PME). Further, this study examines the mediating role of goal clarity and moderating role of top management support. Methodology: Hierarchical linear regressions were used to investigate the relationships. PROCESS Hayes (2003) Model 7 was used for the moderation and mediation analysis. The data was collected from 322 Pakistani public sector developmental project employees. Findings: The results show that public leadership positively affects goal clarity (ß = 0.049, p < 0.001) and project management effectiveness (0.032, p < 0.001). In addition, goal clarity mediates the association between public leadership and project management effectiveness (0.36, p < 0.001). Furthermore, the strength of the mediated relationship between public leadership and project management effectiveness (via goal clarity) depends on top management support. The indirect effect of public leadership on project management effectiveness is high when top management support is high (compared to low). Conclusion: The role of public leadership contributes significantly to the project's success. The project leader recognises, enlists, and promotes the organisation's core competencies, identifies, corrects, and controls key rigidities, places a high value on goal clarity, and continually lines up procedures with the project's overarching goals. Implications: Public leadership is crucial in project management effectiveness, especially in the public sector, where projects often involve multiple stakeholders, limited resources, and complex regulatory requirements. Effective public leadership ensures that projects are aligned with the organization's mission and goals and carried out efficiently, on time, and within budget.