The article highlights and discusses aspects about the initial perceptions of Computational Thinking of a group of Mathematics teachers in K-12, estimates the contributions of a continuing education course on the subject and addresses possible changes in the participants' way of teaching. The case study was conducted through continuing education course and focused on the application of questionnaires with open and closed questions, as well as reports on the inclusion of activities, by the participants, in their teaching practice. The answers were analyzed from a qualitative perspective and the results obtained point to an initial lack of knowledge of the participants about the subject, especially in their relations with the field of mathematics. The offering of the course led to a significant learning on the subject, development of methodologies for the introduction of Computational Thinking in mathematics classes and reflections on how to teach and learn.