This thesis investigates the presence of information and communication technologies (ICTs), especially the smartphone, in a group of Brazilian families with father, mother and young children in Rio de Janeiro, in dialogue with investigations in other countries due to the lack of empirical studies of this area in Brazil. We conducted a qualitative exploratory survey, from July to December 2017, with 10 families, with children from 3 to 6 years old – 17 adults and 14 children participated in the research. The analysis of the data indicates an ubiquity of mobile technology in parents and children s daily lives. The domestication of technology theory by Silverstone, the media ecology theory by McLuhan and Postman and mediation theory by Martín-Barbero are examples of concepts used to support the macro and micro-social analysis that this study is willing to do. We discuss the reconfiguration of family relationships that have been occurring since the twentieth century, with the weakening of the presence of authority as one of the determining factors of the separation between adult world and children s world, a scenario intensified by the presence of mobile technology. Among the results of our investigation are the predominance of strategy of restrictive mediation on children s ICT use and the frequent use of these devices by the parents as electronic babysitters of the children, in contrast with a discourse of concern with the overuse of these technologies by children – they are using such equipment increasingly early and without adult supervision. The research also shows that, unrelated to this discussion, children mix traditional objects and technological devices in their games, although they do not call smartphones toys, an indication that the cell phone has gained a new symbolic dimension in family relationships.