This dissertation aims to investigate how professors construct identities in the classroom by the speech style adopted, as well as it intends to unveil the discourse that they have about themselves as regards to representation of being a professor in higher education. It has the theoretical principles of Interactional Sociolinguistics, critical Discourse Analysis, Social Psychology, and Sociology. It is a qualitative research, with ethnographic guidelines, which also uses the Ethnomethodological Conversation analysis as an auxiliary methodology. The data were raised through the observant participation, the focal group with professors- collaborators, and individualized session for viewing of data with each one. These methods contribute to the adoption of an emic perspective in this work, based on the triangulation researcher, collaborator, and theoretical fundaments. The corpus of this dissertation is comprised of eight hours, forty-two minutes and eight seconds, which corresponds to five filmed classes, and more eighteen minutes, fifty-four seconds of footage of the focal group. In addition, it was recorded twenty-five minutes of the sessions of viewing audio. The results of this research are: (i) the speaking style more or less formal relates to the actions of projection or negotiation of identities in the classroom, because the professors revealed identities as they assume postures sometimes formal, sometimes informal, according to the situational context; (ii) the professor‘s discourse, though it seems democratic, is hegemonic in the classroom because of the power established by their social role; (iii) the representations of what is to be a professor correspond to more democratic educational theories; however, within limits so the classes can be organized and so students can fulfill their academic duties; (iv) linguistic clues such as conversational markers and lexical choice, as-well-as non-linguistic clues which consist of kinesic movements and proxemics, and suprasegmental clues marked a more or less formal style of the professors-collaborators; (v) negotiations of identity in the classroom occurred in a symmetrical way, when there was less formality, and asymmetrically, when the professor had a more formal style. The main contributions of this study are related to the reflection of professors about the identities projected and negotiated by them, which were identified and developed in this work in association to a certain style. The idea of a fixed identity is no longer a reality in the postmodern world, and the liquid and fluid identity, defined by Giddens (2002) and Bauman (2005), apply to the context of this research, given that professors expressed and revealed more than one identity in both the classroom and in the focal group.