This study aims to identify the impact of strategic planning effectiveness and strategic leadership on the institutional performance of the municipal sector in the Ministry of Interior in the Sultanate of Oman. The importance of the research lies in presenting an integrated and clear picture for the decision-makers in the governmental sector. The study sample includes the employees of the municipal sector in the Ministry of Interior, whether in the Ministry’s general office or in the various offices of the governors, whose number is (2400), with a total sample size of (346) employees selected according to Stephen’s Sampson equation. The study adopted the quantitative method, the questionnaire tool for data collection, and the statistical analysis program SPSS to analyze the data and test the hypotheses. The study concluded that there is a statistically significant effect of strategic planning effectiveness and strategic leadership on institutional performance and that strategic planning effectiveness has the highest impact on institutional performance compared to strategic leadership. The study recommended the necessity of striving to spread the vision and mission of the municipal sector, its values, and strategic objectives by various means and working to regularly amend job descriptions and job tasks in line with the factors surrounding the sector. Keywords: Effectiveness of strategic planning, strategic leadership, institutional performance, municipalities sector in the Ministry of Interior.