This article analyses the role played by female social workers in the process of feminization that took place in the Juvenile Justice in Chile, in the period 1928-1954. The «visitadoras» played a significant role in this process, for two reasons: first, their social reports were crucial inputs for the Court’s decision making which, most of the time, followed the «visitadoras» suggestions of child protective measures. Second, social work was a female profession, which used scientific tools (such as diagnosis and visitation) but which, at the same time, highlighted the importance of the children’s emotional ties with their family and environment. This emphasis on affection also produces a feminization of juvenile justice. To demonstrate our hypothesis we analyzed the speeches on the profession of the social workers themselves, and reviewed the social reports contained in the files of the Santiago’s First Juvenile Court.