We describe the development of the Whole School Food Approach framework and its implementation in 12 European countries participating in the European-funded project, SchoolFood4Change. The framework was developed in 2022 by a multidisciplinary team following an evidence-based approach. Data on implementation criteria were collected through mixed-methods in schools between 2022 and 2025 in 17 cities. Surveys with national project coordinators assessed achievement of bronze-level criteria for each framework component. Implementation scores were calculated based on the number of bronze criteria achieved. Semi-structured interviews with city representatives explored perceptions, challenges, and enablers of implementation. The framework comprised four interrelated components and three scalable levels of progress: bronze, silver, and gold. To date, 549 schools have implemented it. Online surveys from participating cities and schools (n = 109) showed diverse levels of implementation across schools, with 21 achieving bronze-level. Semi-structured interviews (n = 16) identified cross-departmental collaboration, staff capacity, and time availability as main barriers. Political and institutional support was reported as the main facilitator for promoting school food policies. Findings showed a diverse implementation of the framework in participating European countries. Despite challenges, the Whole School Food Approach was perceived as a valuable tool for developing healthy and sustainable school food systems.