Gender identity and roles are two of the most complex and important aspects of sexuality, as they define how people should think, feel and behave within society according to the gender they identify with. They are formed from the experiences, beliefs and evaluations that each person makes from childhood about what it means to be a man or woman in a society, which is influenced by both the socio-historical context and the biological factors of sexuality. Adolescence is the critical period of development when great bodily and psychological changes are faced, which forces people to behave according to their sexual nature and the acceptance (or non-acceptance) of the gender culturally associated to their genitals. Social representations (SR), in turn, allow us to understand how collective thought is formed around a specific phenomenon and how the social context influences the construction of beliefs. Thus, this study has set out to describe the SR of gender identity and roles in a group of adolescents in a secondary school in Mexico. To achieve this goal, the research has been framed within the qualitative paradigm, working under the phenomenological design from the process approach of SR. A projective technique of incomplete sentences was used to access the beliefs of the adolescents who participated in the study. The instrument used was the Incomplete Sentences on Sexuality of the Colombian Institute of Family Welfare, which is composed of 10 reagents that explore gender identity and the behaviors related to it. The sample consisted of 73 students aged 12 to 16 years from a secondary school in the city of Santiago de Querétaro in Mexico. A thematic analysis was carried out to identify the codes, categories and subcategories present in the students’ responses, and finally the method of consistency checking was applied based on the review and analysis made by another coder of the results obtained in order to guarantee the objectivity of the study. In this way, the categories of gender identity and cultural gender roles were obtained, within which subcategories emerged that encompass the concepts of masculinity and femininity for the participants, as well as the disadvantages associated with these two genders for the first and the second categories (roles, professions and behaviors that are prohibited for men and women). Among the results, it is evident that the SR of most adolescents around gender identity and roles have been constructed under the sex/gender system and have been influenced by what they have seen or heard from their parents at home. Therefore, the behaviors they believe they can perform are linked to the gender stereotypes they have included within their belief systems and values. This shows that for most participants sex and gender are synonymous, implying that people’s behavior, roles, attitudes and characteristics are defined by the sex they are born with, in which men are superior and women are inferior. According to this analysis of the narratives expressed by the participants, it was found that a small group are included within what has been called the “new masculinities”. Finally, it is worth mentioning that the novelty of the research is represented by the instrument and technique used, which allowed the participants to know how everything they have seen and heard in their homes has influenced their definition of what it is to be male, female and the roles of people in society according to their gender. It is recommended that more studies be done in the future on the construction of gender in adolescents, since it continues to be an issue of social tension and inequality in Latin America and throughout the world. https://doi.org/10.16888/interd.2022.39.2.10