This study examined the relationship between interactive participation, collaboration and project success among NGO health projects in Kumi district. The study was a cross-sectional research design which applied a quantitative research approach. A sample of 44 health projects in Kumi District. Primary data was obtained from a project manager, program manager and monitoring & evaluation officer using a structured questionnaire. SPSS v. 25 was used to analyze data, and results were presented and interpreted using frequency tables, correlation, and regression analyses. The study found a positive relationship between interactive participation and project success. A positive relationship between collaboration and project success was also obtained. The study also found that collaboration was a partial mediator in the relationship between interactive participation and project success. Moreover, this study found that interactive participation and collaboration were significant predictors of project success. Moreover, this study established that interactive participation was a better predictor of project success among health projects. The study concludes that interactive participation and collaboration are inevitable in stimulating project success among health projects. It equally concludes that health projects will be more successful when they mainly focus on interactive participation. The study recommends health projects to intensify interactive participation, and strengthen collaboration with stakeholders to boost project success.