The objective of this study was to examine the effect of participatory project design on project success in a government-funded project in Uganda, a case study of Parish Development in Kabale District. A cross-sectional survey was done. 75 respondents provided information, and we integrated quantitative and qualitative analysis. The analysis was conducted on three separate levels and included descriptive, bivariate, and multivariate approaches. The bivariate correlations between the dependent variable and the predictor components were examined using a Pearson correlation matrix. The dependent variable was regressed against the revised predictor factors at the multivariate level (project success). An analysis of the data was done using a linear regression model. Results of the regression analysis demonstrate that participatory project design has a beneficial effect on the effectiveness of parish development models in the Kabale District (coef = -0.780, p-value = 0.000). The main conclusion of this study is that parish development model project success in Kabale district is significantly influenced by participatory project design. In order to guarantee the sustainability of the project success of the parish development model, the study suggests that more emphasis should be placed on adopting participatory project design through defining project goals, determining results, identifying risks and constraints, and refining project strategy.