The issue of academic achievement among pre-service teachers in Nigeria has garnered significant scholarly attention due to its implications for the overall quality of education in the country. Research attributes poor academic performance to the predominant use of conventional instructional approaches, which are often inflexible and promote passive learning. This study examined the effect of a blended Universal Design for Learning (UDL) intervention on the academic achievement of pre-service teachers. Results from the Welch t-test indicated a statistically significant difference in mean scores between the Experimental Group (M = 73.58, SD = 12.14) and the Comparison Group (M = 68.24, SD = 13.85), t(244.202) = -3.238, p = .001, d = -0.41. Additionally, analysis of covariance (ANCOVA) revealed a significant group effect, F(1, 246) = 10.595, p = .001, η² = .041, with the Experimental Group demonstrating higher marginal means (M = 73.57, 95% CI [71.278, 75.864]) compared to the Comparison Group (M = 68.24, 95% CI [65.979, 70.510]). These findings suggest that the blended UDL intervention significantly improved academic achievement, yielding a moderate effect size (η² = .041). The implications for educational practice and future research are discussed.