This research aims to understand the participation of women within the Brazilian union policy, through a case study about the workers union of the Fundação Oswaldo Cruz (Fiocruz), Asfoc-SN. This union has always had the presence of women in positions of power; however, the research aims to understand what changes bring to the union movement, predominantly male, with female protagonism. The main hypothesis: the presence of women in management positions at Asfoc favors their presence on union agendas and events was developed through a bibliographic investigation, data analysis and interviews with the main union leaders of Asfoc-SN. To investigate whether, in fact, with the female presence occupying leadership positions in the Fiocruz civil servants union, there was a change in looking at specific guidelines of the women of the Oswaldo Cruz Foundation. The hypothesis is partially confirmed, since only with the entry of a woman in the presidency of the Fiocruz institution and not necessarily in union positions, according to the data analyzed, there is some change in the way of portraying women and, consequently, in the change of agendas. However, the female presence gains some prominence and the directors see the need for transformation after the occupation of these positions by some women. It is possible to highlight the relationship between men and women in these union leadership positions and how disputes occur within this arena of power whose ultimate objective is to protect workers and improve their living and working conditions.