Within the dynamic realm of competency-based education, the establishment of meaningful and engaging learning environments is crucial. Consequently, there has been an increasing scholarly interest in exploring the utilization of games in teaching and learning. However, most games in recent research aim to engage students in practice-and-drill activities. Our research focuses on the application of manually designed learning games, based on the Experiential Learning Theory, within a primary school in Ho Chi Minh City, involving 208 third-grade students. Using a quasi-experimental design with a pre-post intervention evaluation, the study aims to assess the impact of these games on students' academic performance in mathematics and their motivation towards the subject. The findings, derived from quantitative data analysis, reveal significant improvements in both academic performance and motivation post-intervention. This research contributes to the growing body of knowledge on gamified learning and offers practical methods to integrate student engagement. It underscores the value of well-structured, theoretically grounded learning games as an effective tool in modern educational practices, especially for complex subjects like mathematics at the elementary level.