This study developed and evaluated an interactive Digital Textbook (DT) to improve genetics learning among 10th-grade students in Tanzania. Traditional approaches to genetics instruction often present abstract content that limits student engagement and understanding. To address these issues, the DT was created using the Genially platform, incorporating multimedia and interactive features to promote active learning. The development followed the ADDIE model: analysis, design, development, implementation, and evaluation. A true experimental design with 30 secondary school students compared outcomes between an experimental group using the DT and a control group using print-based textbooks. Results revealed that the experimental group achieved significantly higher post-test scores (M = 7.49, SE = .46) than the control group (M = 6.05, SE = .46), F (1, 27) = 4.89, p = .036, η² = .153. In addition, students using the DT reported greater learning satisfaction. Qualitative feedback highlighted the effectiveness of multimedia and interactivity in enhancing understanding of complex genetic concepts. These findings support the integration of interactive digital tools in science education and call for investments in digital infrastructure, teacher training, and the development of high-quality digital content to support broader implementation.