Resumo. The following study presents an exploratory qualitative research that was carried out with 47 high school teachers who work in different public schools. Teachers’ professional development is a process that depends on several elements that are within not only the academic scope or the number of academic degrees one has as it happens in initial teacher training, but within continuing professional development as well. Therefore, it is understood that it is the role of the 21st century teacher to invest in his/her training to obtain personal and professional development, and with that, to contribute to the teaching and learning process, and consequently improving the quality of education. Then, the reason for writing the paper is based on the following question: How teachers, by seeking professional development, can improve professionalism within teaching? The study analyzed the professional development of teachers who work in different public high schools. The data were collected from a questionnaire sent by e-mail that allowed the content analysis under the perspective of Bardin (2011) with the help of Atlas Ti software. It was possible to identify that high school teachers develop themselves professionally from the difficulties experienced in the school, specifically, by the lack of technological knowledge. Such fact makes them to look for training, which contributes to their professional development.