Urban public spaces are arenas in which cultural and communicative patterns of encountering others are reproduced through the unwritten rules of everyday interaction. As one of the most densely populated urban spaces, the metro places individuals in situations of co-presence with strangers, requiring the continuous regulation of modes of presence and levels of communicative involvement. The present study aims to explain how social presence is managed in the metro through a qualitative approach and grounded theory methodology based on the Strauss and Corbin approach. The participants included 18 metro passengers selected through theoretical sampling. Data were collected through semi-structured interviews and field observations and were analyzed through open, axial, and selective coding processes. The findings revealed that participants employ a set of behavioral strategies to maintain interactional order and prevent social misinterpretations, which were organized into five axial categories: 1) surveillance without assuming the role of an observer; 2) management of potential accusations; 3) preventive distancing; 4) negotiation between curiosity and self-restraint; and 5) producing invisibility in a dense space. These categories ultimately led to the core category of “regulating presence in co-presence with strangers”. The findings indicate that communication in public spaces emerges through the relationship between communicative actions and practices of presence management, whereby individuals organize their interactional boundaries through the regulation of their own behavior. Accordingly, communicative order in the metro is a process that is sustained through the continuous alignment of individuals’ behaviors with cultural expectations and the unwritten rules governing encounters with strangers.