Teaching engineering at the middle and high school levels has been a topic of discussion among scholars regarding the challenges it creates. One of the most critical challenges at the school level is identifying qualified teaching staff to lead engineering courses. The present study explored teachers’ willingness to lead an engineering course and the reasons behind their willingness or unwillingness to do so. The study involved 434 participants, who were enrolled in a STEM professional development program and were diverse regarding their teaching subjects, the grade levels they taught, and the locations of their schools in Turkey. In this mixed-methods study, researchers collected data at the beginning of an online professional development program. Quantitative data were analyzed descriptively, while qualitative data were analyzed with a data-driven codebook. Almost two-thirds of the participants were keen to teach an engineering course, yet differences were observed according to the subjects they taught and their professional backgrounds. Most of the mathematics teachers, the group with the highest percentage of willingness, seemed to have a holistic approach towards engineering, with half emphasizing collaboration between teachers and engineers. The study provided further insights into how initial teacher training and continuous professional development programs can be structured based on teacher expectations and needs.