Assertive Community Treatment (ACT) is the most common ambulatory service delivery model for people with severe mental illness worldwide. Flexible ACT, a Dutch modification of ACT, provides comprehensive care for the entire population of people with severe mental illness (SMI). FACT combines the principles of individual case management with ACT services. Researchers found an association between model fidelity and treatment outcome. Consequently, scholars formulated fidelity scales based on previous research and expert opinion (operationalizations of multiple criteria of team structure, organization and treatment processes). The first FACT model fidelity scale from 2008 facilitated the dissemination of FACT and prevented programme drift. Ten years later, an update was necessary to address relevant local variations in implementation, due to specific population profiles and available regional network services, and to improve recovery-oriented and evidence-based practices. Authors and stakeholders tested and updated a new FACT-model fidelity scale in the Netherlands, Denmark and Sweden. The resulting scale assesses 16 quantitative items and 8 qualitative, descriptive topics on 5-point Likert scales. The scale includes FACT-criteria that evidently work and still allow a team to diversify. The FACTs 2017 is a new standard to assess FACT-team model fidelity for the care of people with severe mental illness in The Netherlands and Scandinavia.