This thesis presents a discussion of the designer’s action. This involves, fundamentally, the designer s effort in becoming a professional and make design. I use an ethnographic perspective to see this movement. So, I took the discourse and experience of the designer. To that end, I conducted a study of six months, when I ve been living with designers in a design office. During this period, I followed designers developing a project of a tricycle for a big automotive company. Following the daily lives of designers, the design action gradually ceased to be restricted to technical operations, and began to reveal a passionate game, marked by conflicts, negotiations and transformations that affect all actors involved, changed office’s rhythms and dynamics, and modified the product design.