Nigeria, despite its vast natural and human resource endowments, continues to struggle with persistent poverty, institutional decay, and underdevelopment—challenges largely attributed to widespread corruption. Over 71 million Nigerians live in extreme poverty, while food insecurity and poor human development indices remain prevalent. This study critically appraises the role and effectiveness of the Economic and Financial Crimes Commission (EFCC) in combating corruption in Nigeria between 2012 and 2022. Drawing upon the Institutional Theory by Douglas North, which emphasizes the influence of formal and informal institutional frameworks on societal behavior, the study analyzes how institutional weaknesses and governance failures impact anti-corruption efforts. A descriptive research design was adopted, utilizing both primary data from in-depth interviews with six notable Nigerians and secondary data from academic and official sources. Findings reveal that although the EFCC recorded notable achievements, such as increased conviction rates from 103 in 2015 to 3,785 in 2022 and some asset recovery successes, corruption remains systemic and deeply embedded in Nigeria's public sector. Institutional bottlenecks such as constitutional immunity for political officeholders, judicial inconsistencies, executive interference, and operational inefficiencies significantly limit the EFCC’s autonomy and effectiveness. Key anti-corruption strategies such as the whistle-blowing policy, asset declaration regime, forensic accounting, and the implementation of the Bank Verification Number (BVN) while theoretically promising, are undermined by poor implementation, low public trust, weak legal protections, and capacity constraints. Interviewees highlighted perceptions of selective prosecution and political bias, further eroding confidence in the Commission's neutrality and impact. The study concludes that while the EFCC has made measurable progress in Nigeria’s anti-corruption fight, meaningful eradication remains elusive without comprehensive institutional reforms. Recommendations include amending constitutional immunity provisions, granting the EFCC full operational and financial autonomy, strengthening whistle-blower protections and asset verification mechanisms, and establishing a dedicated forensic accounting directorate. These measures, grounded in the Institutional Theory framework, are essential for fostering transparency, strengthening governance structures, and achieving sustainable anti-corruption outcomes in Nigeria.