The purpose of this study was to investigate flow experience and situational interest in a math learning game that included adaptive scaffolding. Fifty-two Finnish 5th graders played the game about fractions at home during COVID-19 enforced distance learning. The results showed that flow experience correlated positively with situational interest. Importantly, a deeper analysis of the Flow Short Scale (FSS) subscales revealed that only absorption by activity but not fluency of performance explained variance in situational interest. That is, at least in game-based adaptive learning, situational interest is mostly related to immersive aspects of flow. Results also revealed that students with better in-game performance had higher flow experiences, but their levels of prior knowledge were not related to flow levels. In contrast, students with lower prior fraction number knowledge showed higher situational interest, which might be partly attributed to the additional game elements provided to struggling students in the form of adaptive scaffolds. Moreover, the study demonstrated that the developed adaptive scaffolding approach and in-game self-reporting measures worked well. Finally, the implications of these findings for flow experience and situational interest research in game-based learning context are discussed.