This study focuses on exploring the beliefs regarding the construction and development of Teacher's Professional Identity (TPI) of Secondary Education Master's Degree (SEMD) students from the areas of Science and Technology. An 'S-TPI' questionnaire, measured using a Likert scale, was used to obtain the opinions of 279 future teachers in the 2014-2018 academic years. After analysing the data, no significant differences were found between the two groups (Science and Technology). However, there were significant differences in the responses obtained for the four dimensions on the scale with regard to the students' gender. We noticed an important relationship between the global view of professional identity and the development of educational skills linked to socio-educative and methodological aspects. These results may contribute to improving knowledge concerning future teachers' beliefs and have served as a basis on which to design activities that will enable us to integrate TPI into the initial training process.