Abstract: This study examined the influence of project implementation strategies on the performance of the Kigali Informal Settlement Upgrading Project (KISUP) in Nyarugenge District, Rwanda. It assessed project design, stakeholder engagement, resource management, and monitoring and evaluation in relation to project performance. Guided by Stakeholder Theory, Contingency Theory, and Goal-Setting Theory, the study adopted a descriptive and correlational mixed-methods design. The target population comprised 477 KISUP stakeholders, with 217 sampled. Data were collected from 164 questionnaire respondents and 27 key informants. Quantitative data were analyzed using descriptive statistics, Pearson correlation, multiple regression, and ANOVA, while qualitative data were analyzed thematically. Results indicated high agreement on project design (M = 4.27), stakeholder engagement (M = 4.25), resource management (M = 4.27), monitoring and evaluation (M = 4.28), and project performance (M = 4.26). All four strategies correlated positively with performance. The regression model was significant, F(4,159) = 76.614, p < .001, explaining 65.8% of performance variance (R² = .658). Project design was the strongest significant predictor (β = .617, p < .001), followed by monitoring and evaluation (β = .356, p < .001). Stakeholder engagement and resource management were not significant independent predictors. The study concludes that effective front-end design and continuous monitoring are critical to KISUP performance. It recommends comprehensive planning, stronger feedback-oriented M&E, sustained stakeholder participation, and improved resource coordination.