This study was carried out to analyze an online science, technology, engineering, and mathematics (STEM) teachers’ professional development using the DEmonstration, CO-train/design/teach, DEbrief (DECODE) model to empower teachers in refining technological pedagogical content knowledge (TPACK) skills. The model was performed due to the focus on STEM education as well as the ongoing challenges posed by the virtual environment era. The online DECODE model is mainly based on virtual lectures in combination with hard copies of instructors’ manuals, forming a blended training model. Therefore, the model empowered teachers to refine TPACK skills through familiarization with various software technologies and enhancing proficiency in instructional design. A total of ninety-one teachers from diverse educational settings, including urban, suburban, and rural schools, actively participated in a comprehensive 72-hour study. A willingness to engage in similar STEM-TPD sessions in the future was expressed after the analysis of open-ended questions. Furthermore, the paired sample t-test results showed a significant difference in TPACK ability before and after the training (t = 4.21; <i>p </i>= <.001; <i>d </i>= .82). The results showed that online teachers had increased the understanding and ability of TPACK after participating in online STEM-TPD workshop. Therefore, STEM-TPD with the DECODE model was essential to preserving teaching quality in the virtual and digital age.