Abstract: Construction delays have become a key contributor to project failure in Rwanda. The primary purpose of this research was to assess the effect of sustainable local materials management on the success of Gisozi Affordable Housing Project in Gasabo District. The theoretical framework was anchored in the Resource-Based View theory, Stakeholder Theory, the Triple Bottom Line framework, and Sustainability Theory. A descriptive and correlational research design was implemented, utilizing both quantitative and qualitative approaches. The study population consisted of 227 professionals from major housing developments, with a sample size of 145 respondents selected using Slovin’s formula through stratified and simple random sampling. The regression results showed that sustainable local material planning practices had a positive and significant effect on the success of Gisozi Affordable Housing Project in Gasabo District with B = 0.150, t = 2.459, and p = 0.015, while sustainable local material procurement had B = 0.489, t = 10.188, and p = 0.000. Sustainable local material quality management had B = 0.132, t = 2.694, and p = 0.008, whereas sustainable local material monitoring and evaluation had B = 0.194, t = 2.812, and p = 0.005. The study concludes that sustainable local materials management significantly improves project success, especially when procurement systems, planning controls, quality checks, and monitoring practices are strengthened. The study recommends that Gisozi Affordable Housing Project managers should institutionalize a formal local materials management framework linking supplier rating, delivery tracking, quality testing, and milestone audits to improve project success.