Despite the benefits of integrated Science, Technology, Engineering, and Mathematics (STEM) education that have been discussed for decades; many teachers still find it challenging to implement integrated STEM education due to lacking confidence and experience. Numerous models and frameworks exist, but they tend to focus on enhancing teachers' conceptual understanding rather than providing concise, step-by-step guidance for implementation. An urgent demand for a conceptual model to fit teachers' practical teaching needs has been yielded. The current study aims to reach agreement among Integrated STEM Education professionals on an instructional design model that teachers could follow when teaching integrated STEM education. An online Delphi study was conducted to collect data from a panel of 12 experts from different countries. Consensus and stability were achieved to ensure its validity from international perspectives. The results revealed an integrated STEM education instructional design model with six stages, namely Preparation, Analysis, Design, Planning, Implementation, Evaluation (PADPIE), and 25 tasks. The six-stage PADPIE model was proposed as guidance for teachers to organize well-structured activities in integrated STEM education; the tasks were formulated into a checklist that allows teachers to examine their works.