act In the study herein the authors adopted the framework of technological pedagogical content knowledge (TPCK) and the approach of technology mapping in order to teach secondary education computer science teachers how to teach with technology. During a 15-hour teacher professional development program, teachers learned how to think about the educational affordances of different computer tools, and how to use them to make computer science content more understandable to learners. In addition, teachers learned how to think iteratively about technology, content, and pedagogy in order to design learning activities appropriate for learners' conceptual ecology. The study presents good examples of TPCK in practice by demonstrating teachers' actual instructional artifacts as these emerged through their participation in the teacher professional development program, as well as their evaluations of the program.