This study examined the boredom–creativity link by including students’ levels of over- and underchallenge. Based on the Meaning and Attentional Components model and the Cognitive Load Theory, we proposed the negative effects of students’ boredom combined with being overchallenged on creativity, whereas boredom combined with being underchallenged might enhance creativity. We examined this hypothesis in mathematics classes in a sample of N = 119 German high school students (Mage = 13.86, grade 8). A random slope approach to interaction modeling was used to investigate the effects of boredom and overchallenge and of boredom and underchallenge. The results revealed significant interaction effects in the postulated directions and no conditional effects neither of boredom nor of over- or underchallenge on the first creativity task. Hence, higher levels of boredom combined with higher underchallenge were related to increased mathematical creativity, whereas higher boredom combined with higher overchallenge reduced creativity on the first task but not on tasks two and three. The study provides insights into how cognition and emotion interact regarding learning and creative behavior and offers practical implications for understanding how students experience boredom, particularly in relation to being either over- or underchallenged. This understanding can clarify the attentional and motivational consequences of this prevalent emotion, especially in mathematics.