Education for sustainable development (ESD) faces significant implementation challenges in science, technology, engineering, and mathematics (STEM) classrooms, including limited hands-on learning tools, disconnected curricula, and insufficient teacher training in sustainability integration. This study addresses these gaps by developing and evaluating the ESD I-STEM module, a novel approach that integrates ESD, STEM, and digital learning tools to teach biodiversity. Designed using the ASSURE instructional model and adopting a mixed-methods design, the module incorporates digital comics, interactive games, digital posters, and problem-based learning (PBL) to enhance student engagement, digital literacy, and sustainability awareness. Expert validation by eight specialists confirmed the module’s excellent content validity (95%), significantly exceeding standard benchmarks. Reliability analysis of student responses showed strong internal consistency (Cronbach’s alpha=0.820). Practical implementation revealed high usability, with mean evaluation scores ranging from 4.43 to 4.93 on a 5-point Likert scale. The ESD I-STEM module effectively addresses key gaps in sustainability education through a well-validated and classroom-ready framework for ESD-STEM integration. Results demonstrate its effectiveness as a rigorously tested and usable educational resource that promotes meaningful engagement with sustainability concepts while supporting STEM learning objectives. This study offers educators a proven model for delivering integrated ESD-STEM instruction that prepares students to address real world environmental challenges.