Over the past few years, the world's attention has been focused on gaming systems and their application in education through gamification, incorporating game features into learning tools. Against this backdrop, this study aims to investigate the motivation of EFL learners in a Gamified Formative Assessment (GFA). Theoretical insights from self-determination theory (SDT) are synthesized in the context of motivation analysis and internalization. Data from interviews and questionnaires are collected, and pair-t-tests and basic linear regression, CiteSpace, are utilized for data evaluation and literature review. Paired t-tests for the control group (CG) and the experimental group (EG) in the first and second stages, as well as the EG's first and second stages, show a strong positive correlation between CG's scores in stages one and two and EG's scores in both stages (r1 = 0.930, r2 = 0.851, r3 = 0.953, p < 0.001). It is found that Quizizz, as an example of GFA, can enhance EFL learners' internalization at a higher level during their learning process. Furthermore, our findings also suggest that gamification enables most EFL learners to recognize the value and benefits of assessment as motivation for identified regulation. Additionally, the overall accuracy of the students in the EG, which is 89.05%, is higher compared to the CG's accuracy of 74.01%. It is interesting to note that their motivation level correlates with their performance and engagement. With these findings, we contribute to the literature by validating that gamified formative assessment fosters the internalization of EFL at the elementary level, thereby enhancing students' engagement and language proficiency. Therefore, as one of the studies on gamification and motivation, this research holds unique value in analyzing EFL instruction at the primary school level.