The challenges of disciplinary integration in teaching practice, especially in the implementation of tasks that promote interdisciplinary approaches, highlight the importance of teachers' professional knowledge in this process. Using a naturalistic approach, this study aims to characterize the professional knowledge of a physics teacher when adopting an interdisciplinary approach using technology. The results of the research revealed that the teacher mobilizes different types of knowledge, showing a differentiated knowledge of the most appropriate mathematical application to teach a given piece of content, and knowledge of how pedagogical strategies can be aided through different applications using technology.