Corruption remains a deeply entrenched structural problem in many Islamic countries, despite religious teachings emphasizing ethical behavior and integrity. This study examines the influence of religion and socio-economic factors on corruption levels in 53 member states of the Organisation of Islamic Cooperation (OIC) in 2020. Employing a quantitative approach using Ordinary Least Squares (OLS) regression, it focuses on two religious indicators: the proportion of Muslim population (religiosity) and the status of Islam as the official state religion. The findings reveal that religiosity does not significantly affect the Corruption Perceptions Index (CPI). However, institutionalizing Islam as a state religion has a positive and statistically significant impact on CPI, indicating that countries with an official state religion tend to have lower corruption levels. This suggests that when religion is formally embedded within the institutional framework, it may enhance public governance. Furthermore, socio-economic variables such as economic freedom, political stability, and GDP per capita also play a significant role in promoting transparency and accountability. These findings highlight the importance of institutional quality in combating corruption and imply that beyond moral values, institutional reforms are crucial for developing effective anti-corruption policies in Islamic countries.