The electronic Dynamic Appraisal of Situational Aggression combined with the Aggression Prevention Protocol (eDASA+APP) is a clinical decision support system designed to prevent aggression, reduce coercive practices and promote proactive nursing interventions. It has previously been tested in forensic psychiatry in Australia. Adaptation and feasibility testing are required before implementation in new clinical and linguistic contexts. The aim of this study was to examine the feasibility of the Finnish version of the eDASA+APP using a mixed methods approach. The study took place in four Finnish mental health inpatient units. Nurses completed an online learning module and used the eDASA+APP for 2 weeks. Quantitative and qualitative data were collected on nursing documentation and feasibility. As a result, the eDASA+APP was perceived as easy to use and helpful in establishing a shared process and terminology for aggression prevention. Documentation of risk assessments and preventive interventions increased. The e-learning module was considered adequate. One unit caring for older adults found the risk assessment component less practical. The Finnish eDASA+APP appears feasible and beneficial, supporting a larger implementation in units with adult patients. However, the feasibility testing in older adult services is recommended. The Mixed Methods Reporting in Rehabilitation & Health Sciences checklist was followed in reporting this study.