The main aim of this paper is to reconstruct the process of becoming a caregiver working in early childhood and care (ECEC) daycare centres for children up to three years of age in Poland. The theoretical framework is the concept of becoming, through which the formation of professional identity, within the social world of the nursery, is reconstructed. The process of becoming a nursery caregiver takes place within a specific historical, political, social, institutional and interactional context. Reflexively created self-identification requires confirmation by interaction partners. New empirical data were collected through the thematic narrative interview technique (n = 55) focused on the professional experiences of women caregivers. Data coding and analysis were conducted according to the grounded theory method. Based on an in-depth analysis of the narrative interviews, the process of becoming a caregiver in a nursery was reconstructed, which includes preparing for the role, building professional practices in the context of the nursery's concept of work and creating a professional identity. Due to the institutional framework of the process of becoming a caregiver, the results of the study are discussed in reference to the Polish ECEC context.