This paper presents a method that instructors have designed and implemented to form balanced teams based on Belbin’s roles, with the aim of boosting positive interdependence and individual accountability within the teams and improving their performance in a project-based learning environment. Students’ performance has been measured through the scores obtained during the project, individual exam and Individual Accountability Factor (IAF) and compared with cohorts of previous years, in which team composition was self-selected by students. Belbin teams (18/19–19/20) have performed significantly better than self-selected teams (16/17–17/18). Additionally, students’ feedback experience and opinion has been collected. Students belonging to Belbin teams acknowledge that they attend classes more regularly, they need less time for study outside the classes and they show a higher interest for the subject at the end of the course. They also agree that working on Belbin teams has helped them to mainly improve interpersonal relationships and social skills, followed by positive interdependence and individual accountability. This team forming method gives students the opportunity to identify their own strengths and weaknesses and understand the roles (behaviours) of their teammates as well as their strengths and weaknesses. Besides, it encourages learners to focus explicitly on group work skills.