© 2019, © 2019 Taylor & Francis Group, LLC. The efficiency of interventions in addiction is associated with the processes of practitioners’ professional development. Identity formation is studied extensively for clinical professions but little research focuses on social workers working in addiction settings. This study examined the experience of social workers working in a community treatment network in Greece. Fifteen interviews were conducted with 11 women and 4 men, ranging between 29 and 47 years οf age, who worked in different centers within the network. Data were analyzed following the guidelines of Interpretative Phenomenological Analysis, offering in-depth examinations of people’s lived experience. The results delineate a series of transformations in professional identity comprising a process of biographization. The participants highlighted intrapersonal and relational factors that influence this process which leads to self-understanding and engagement with the therapeutic community. The results contribute to deciphering the factors that influence social workers’ experience in their professional identity formation in substance abuse treatment contexts.