Several studies have revealed contextual tensions in the lives of children and young people going through cultural transitions. However, despite the necessary adaptations, many migrant children have had a good performance in their schooling processes. Considering Bronfenbrenner’s ecological framework and bio-psychosocial approach and using the “Day in the Life” approach, the aim of this chapter is to identify and analyse the experience of cultural transition and acculturation of an eight-year-old boy who, having moved from Bahia with his parents and sister, currently lives in the city of São Paulo. Caio is considered to be a successful case in this process of cultural transition, given his adaptation to the school and community environments, and his good performance in developing literacy and in the socialisation process. The research indicated mutual influence of events experienced at school and with his family, especially through imitation, resulting in a positive cultural interlocution between these two ecological contexts. It was observed that the child felt great satisfaction when presented with opportunities to apply what he learned at school in his family’s everyday life, during play, with electronic games, and in the family context. The study also examined the importance of the family as an ecosystem which preserves the previous culture, offering support and security for a successful introduction and appropriation of the new culture, allowing him to overcome challenges and resulting in the integration of the inherited and of the new ecosystems.