Aim: Specialized early intervention (SEI) treatment in meta-analysis has proven to be effective, compared to usual treatment, in treating first-episode psychosis, and the dissemination of SEI services is increasing. A prerequisite for upholding positive effects is to ensure fidelity to the treatment concept once tested. The aim of this study was to map programme fidelity of SEI teams in Denmark by testing a newly developed fidelity scale. Methods: The 18-item SEI fidelity scale was assessed by visiting SEI teams in person. The scale is divided into 2 dimensions: one concerning the structure and the other concerning the character and content of the treatment. Interviews were conducted with team leaders, patients and members of the staff, and team conferences were observed. Satisfactory fidelity can be obtained at 2 levels: an elite level and an adequate level. Results: In total, 96% (n =22) of the Danish SEI teams participated in the fidelity study. An elite fidelity score was achieved by 32% of the teams, scoring 15 or 16 on the 18-point scale; 27% reached adequate level. With regard to the structural domain of the scale, we found variation among the teams. Conclusions: The multimodal approach was found to be very efficient in evaluating elements critical to SEI teams in Denmark. A low score on the structural domain could, in the long term, lead to an inability to maintain a well-functioning team and provide high-quality treatment.