Many studies have shown the positive impact of serious educational games (SEGs) on learning outcomes. However, there still exists insufficient research that delves into the impact of immersive experience in the process of gaming on SEG-based science learning. The dual purpose of this study was to further explore this impact. One purpose was to develop and validate an innovative measurement, the Game Immersion Questionnaire (GIQ), and to further verify the hierarchical structure of game immersion by construct validity approaches, including exploratory factor analysis (EFA) (n?=?257) and confirmatory factor analysis (CFA) (n?=?1044). The second purpose was to investigate the impact of game immersion on science learning through SEG play (n?=?260). Overall, the results supported the internal structure of the GIQ with good reliability and validity, and the inter factor bivariate correlations for each construct indicated a high internal consistency. Players did learn from playing an SEG, and game immersion experience did lead to higher gaming performance. Moreover, players' gaming performance plays a role in mediating the effect of immersion on science learning outcomes through SEG play. However, as players became more emotionally and subjectively attached to the game, the science learning outcomes were not definitively reliable.