This study employed a difference-in-differences analysis technique to estimate the average treatment effect of automatic promotion on students' cognitive learning outcomes in Uganda's primary education. Regression results indicate a positive policy effect on learning achievements in literacy and numeracy at primary three (P3) and primary six (P6). Specifically, the implementation of automatic promotion policy has translated in to an increase in learning outcomes in reading and mathematics at P3 and P6, all statistically significant at conventional levels. Decomposing the effect along gender and school location (rural or urban) dimensions reveals positive and statistically significant effect on literacy and numeracy in both grades. The effect on students' scores in rural areas is higher than that on students' in urban schools. In terms of gender, the effect is relatively similar for female students and their male counterparts. These results are contrary to the popular belief among many Ugandans, but consistent with earlier scholarly works that have attributed automatic promotion with positive impact on learning outcomes.