STEM (Science, Mathematics, Engineering and Technology) education has widely been considered to have the potential to prepare students with 21st-century skills. Though the Government of Bangladesh (GoB) is concerned with developing human resources for the 21st-century, STEM education has not yet achieved a strong position in the national curriculum system. This study aims to provide a guideline to the GoB to take necessary steps to integrate STEM initiatives aligned with the current science and mathematics curriculum. Adopting a literature survey on the integrated STEM approach, document analysis (primary math and science curriculum, textbook, and teachers' guide of grade 3, 4, and 5) and semi-structured interviews of the primary mathematics teachers, head teachers, STEM experts and curriculum developers of Bangladesh, a framework of integrated STEM approach for primary level has been developed. Besides, the study identified some chapters from science and mathematics textbooks where there are some scopes to integrate the STEM approach and also developed some STEM activities for grade 3, 4, and 5 as future guidelines to the practitioners. This study contributes to the field of STEM-focused primary education in the context of Bangladesh by offering practical guidelines for academic institutions, curriculum developers, teachers' trainers, and policy makers of the country.