Background: Aggression and violence are prevalent in forensic psychiatric inpatient care. These behaviours significantly impact treatment outcomes, work environments for staff, and strain relationships among patients and caregivers. Managing such behaviours poses a formidable challenge that necessitates innovative approaches and evidence-based interventions. The Therapeutic Meeting with Aggression (TERMA) intervention consists of an eight-session staff training program designed to equip staff with strategies to de-escalate patient aggression thus reducing violence and increase patients’ and staffs’ perceived safety. Objective: The aim of this project is to evaluate the violence prevention model TERMA regarding perceived safety by patients and staff and adverse events within forensic psychiatric inpatient care. Additionally, the project will investigate whether the organisational culture affect the implementation of the TERMA model. Methods: The project includes an observational study with a before and after design. Implementation of TERMA consists of an eight-seminar staff training program. Data sources include questionnaires, medical records, and registries. Quantitative data will be analysed with descriptive and comparative statistics. To analyse changes between the measurements, the plan is to use dependent sample t-tests or Wilcoxon-Signed Rank, depending on if data is normally distributed or not. The project will also include qualitative interview studies, which will be analysed using qualitative inductive content analysis. Results: Participant enrollment began in July 2023 and was concluded by the end of 2024. Data collection and analysis of quantitative data are expected to be completed by early 2026, after which the study findings will be submitted for publication in peer-reviewed scientific journals. Collection of qualitative data is scheduled for second half of 2025 and 2026. Conclusions: This study can add valuable knowledge about the effects of violence prevention model TERMA. Clinical Trial: Trial registration number: NCT05932108 International Registered Report Identifier (IRRID): DERR1-10.2196/74295