This study investigates how students' competition preference as a trait variable, in conjunction with students' state self-monitoring, affects learning outcome when learning with a serious game. In particular, it is investigated whether competition preference moderates the relation between self-monitoring and learning outcome. For the study, 86 students (M[subscript age] = 13.39, SD[subscript age]= 0.58) played a serious game to learn about the entrepreneurship of craft enterprises. Competition preference and self-monitoring were assessed using self-report questionnaires. Learning outcome was assessed in terms of students' mental model accuracy (MMA) by using structural assessments of knowledge before and after gameplay. The results show that competition preference significantly and negatively predicts learning outcome, whereas self-monitoring serves as a significant positive predictor. By testing different percentiles of students' competition preference, our findings further indicate that the positive relation between self-monitoring and learning outcome occurs only for students with low to moderate competition preference. These results underline the necessity to take into account students' individual preferences when designing serious games and similar interactive learning environments.