In this article, I intend to analyze the notion of secondary socialization through a specific case study: the French firefighters. This work is based on an in-depth ethnographic inquiry, and I describe the different steps of this social and professional process. I aim to provide a better understanding of socialization by examining the role of institutions, the “learning by doing” process, the rites and the representations of this universe. By reconstructing the practical logic of this social life, I show how a specific habitus of “becoming a firefighter”' is built day after day.