In Switzerland, public child protection agencies are mandated to intervene if a child’s well-being is harmed or threatened and parents are unwilling or unable to remedy thesituation. Child and Adult Protection Authorities (CAPA) decide upon enacting child protection orders (e.g. deputyships) based on a professional assessment of the child’s and family’s situation. Professionals agree that the quality of the assessment is core to the appropriateness and proportionality of the authority’s decision. Yet, no standards on assessment in Swiss public child protection have been established so far. Just recently, a first assessment tool has been published that procedurally structures the assessment linking evidence-based risk and protective factors of child development with the decision to potentially enact child protection orders. The proposed study will analyze how the implementation of this evidence-based risk assessment tool affects the decisional outcome. Furthermore, it will document how professionals handle the new tool, and how processes and attitudes change through handling it. Last but not least, the study will provide findings on how a standardized assessment affects the index child and his/her primary caregiver. The sample consists of 12 CAPAs in the German-speaking part of Switzerland and their caseload. One half of CAPAs will implement the new assessment tools, the other half – matched by size of caseload – will continue with assessment-as-usual. A first work package on decisional outcomes is based on a pretest-posttest study design. Dependent variables analyzed are the invasiveness of child protection orders and the number of repeated referrals. Concerning the assessment of children‘s situations of endangerment, we hypothesize less variance in outcomes for authorities with standardized assessment compared to assessment-as-usual. A second work package focuses on the index child’s health-related quality of life (HRQoL) both self-rated and proxy-rated by the primary caregiver. Furthermore, it will document client satisfaction. Both dependentvariables are collected twice at the beginning of the assessment and its end. In a qualitative-ethnographic approach, a third work package analyzes how professionals perceive the impact of a standardized assessment on their processes and professional discretion. To our best knowledge, this study is the first to empirically evaluate the implementation of a standardized assessment in child protection practice in German-speaking countries – combined with critical qualitative analyses of changes in the authorities’ decision-making context. By providing information on benefits, barriersand disadvantages of standardized assessment it will have direct practical implications.