Financial misconduct within NonGovernmental Organizations (NGOs) in Nigeria has escalated alongside increasing donor funding, yet traditional audit methods remain ineffective in detecting sophisticated fraud. Despite growing scrutiny, forensic accounting—a proactive tool for fraud detection and prevention— remains understudied in the NGO sector, particularly in developing economies like Nigeria. This study addresses this gap by examining the role of forensic accounting in uncovering financial irregularities within Nigerian NGOs, employing a multiple case study approach. Three highprofile cases—the Feminist Coalition, the Hydrocarbon Pollution Remediation Project (HYPREP), and the Ministry of Humanitarian Affairs—were analyzed using forensic techniques, including variance analysis, digital audit trail reviews, and document forensics. The findings reveal systemic weaknesses in financial governance, such as opaque reporting, audit obstruction, and fund misappropriation, which align with the Fraud Triangle and Red Flag theories. Notably, the study demonstrates how forensic accounting can serve not only as an investigative tool but also as a preventive measure when integrated into organizational frameworks. Key contributions include the development of a fraud risk indicator matrix tailored to NGOs and evidence-based policy recommendations for regulators, donors, and NGO leaders. The study advocates for mandatory forensic audits, enhanced transparency, and capacity-building initiatives to strengthen financial accountability in the nonprofit sector. By bridging the gap between theory and practice, this research provides a foundation for future studies on forensic accounting in NGO contexts, particularly in resource-constrained environments.