The Assessment of the Best Interest of the Child and Adolescent is an essential tool to ensure the full protection of the fundamental rights of this demographic, especially in the handling of their personal data. Based on the Statement from the ANPD, which emphasizes the need to consider the best interest as a priority, this assessment proposes a continuous process of analysis and adaptation. It is structured in four main stages: understanding of rights, identification of impacts, assessment of impacts, and creation of action plans. Its application allows data controllers to align their practices with the General Data Protection Law (LGPD), promoting greater security and responsibility in the processing of children’s and adolescent’s data.