STEM education is not a new pedagogical approach in the world, but it would be a new approach in Vietnamese education where students are familiar with learning separated disciplines to acquire academic knowledge in class. To better prepare students about knowledge and skills to adapt to the 4th Industrial Revolution requirements, integrated education of four disciplines, including Science, Technology, Engineering, and Mathematics (STEM), has been promoted in high schools in Vietnam. In the general education program, Chemistry is a subject in the natural sciences group at the high school level (Grade 10, 11 and 12). Chemistry helps students acquire core knowledge about chemistry and apply this knowledge to life. This article aims to clarify the concept, instructional models of integrated STEM education and Project-Based Learning (PBL) - one of the teaching methods commonly applied in integrated STEM education to stimulate students to learn actively and experientially. On the other hand, a combined PBL with the BSCS 5E instructional model to deploy integrated STEM education in a STEM learning project named “Zero waste” of Chemistry 12 is also thoroughly analyzed. Quantitative and qualitative findings on the development of STEM skills of 352 students participating in the “Zero Waste” project in the three-school year at Dao Son Tay high school in Thu Duc City, Vietnam, reveal that their STEM skills were developed. Some minor recommendations on effectively organizing integrated STEM education in Chemistry 12 will be proposed.