BACKGROUND: Objective Structured Clinical Examinations (OSCEs) are amongst the most anxiety-provoking competency assessment methods. An online serious game (OSCEGame) was developed and implemented within the OSCE curriculum. This study aimed to evaluate the usefulness of this serious game on preparedness and reducing OSCE-related stress. METHODS: A serious game was designed to help dental students train for OSCEs. Two game courses (4 stations each) were designed according to year of undergraduate training (4(th) and 5(th) year), based on 6 pre-existing multi-competency OSCE stations. The OSCEGame was available online on a learning platform 4 to 6 weeks before the summative OSCEs. Game use was evaluated by analysing connection data. Preparedness, stress and time management skills were assessed using a questionnaire following the summative OCSEs. The results of 4(th)-year students (OSCE naive population) were compared to those of 5(th)-year students to assess usefulness and benefits of such preparation method. RESULTS: In total, 97% and 60% of the students in 4(th) year and 5(th) year, respectively, used the game. The game was seen as an essential preparation tool to reduce anxiety (for 60% of all students) and increase time management skills (65% of all students). However, significant differences were observed between 4(th-) and 5(th)-year students (anxiety reduction: 65% vs. 22%, p < 0.001; time management skills: 59% vs. 41%, p < 0.05) suggesting that it is most useful for OSCE naive students. CONCLUSION: This serious game is a useful time efficient online tool, for OSCE preparation, especially in OSCE naive students.