The insufficiency of teachers who teach integrative science, technology, engineering and mathematics (STEM) courses is a major challenge facing science education today. Many teachers lack adequate expertise to combine disciplines and choose effective instructional approaches. This study examines how and to what extent teachers might succeed in teaching an innovative STEM program about a sound, waves and communication systems course in an information and communication technology-based environment. This research adopted a qualitative method to understand better the experience of three teachers who taught the course for the first time. Data collection tools included documenting mentoring meetings, observing in the classrooms and interviewing the teachers. The data were transcribed and analyzed using the content analysis method. The findings show that the teachers had only partial knowledge and, initially, even misconceptions about sound. However, their technological pedagogic content knowledge improved significantly due to the researcher's gradual but continual guidance. Four major factors contributed to the teachers' professional development: (a) dealing with innovative contents, (b) using different (advanced) teaching methods, (c) predesigning the instructional course materials and (d) offering the researcher-mentor's developmental supervision.