 The Delphi methodology was used to develop a comprehensive assessment tool for children and adolescents in the child welfare system. The tool consisted of 66 items divided into six dimensions, general information, schools slash work situation, child welfare system history, family visitation history, biological family information, and experiences of sexual abuse. Experts reviewed the tool's format and content throughout its development and validation process. Most of the items performed well, and professionals found them easy to use and relevant. The tool proved to be a valuable and effective tool for collecting sociodemographic information on children and adolescents in the child welfare system, potentially improving their conditions. This article was authored by Olga Fernandez-Garcia, Maria Dolores-Guilario, and Rafael Ballester-Arnold.