Simulated mediation sessions are important for the training of intermediaries in training courses. The use of simulated session methodologies has been measured internationally in other countries, especially regarding the role of the person acting as the child or adolescent. However, there are few studies on the participation of interveners in the practices and evaluation sessions within training courses and their contribution to the development of intermediaries. Following this study, it became evident that the performance of interveners impacts the evaluation of intermediaries. Based on the results, recommendations are provided for performing the role of intervener through best practices.