This action research investigated the effectiveness of integrating the Mystery Box game to improve the academic achievement of grade 10 learners in Probability at a public school in Ozamiz City. The study, conducted in the 2024 school year, employed a classroom-based action research design with 41 purposively sampled participants. Pre and posttests assessed probability understanding, while a comprehensive lesson plan and a questionnaire gathered information on improvements after a game intervention. Statistical analysis included frequency, Percentage, mean, standard deviation, T-test, and thematic analysis. The findings revealed that integrating the Mystery Box game significantly increased learners' academic achievement in Probability. In conclusion, the post-intervention outcomes decisively confirmed the game's effectiveness in enhancing probability learning, fostering a love for learning, and promoting academic performance and social connections. The research recommended consistently integrating game-based learning in Probability, teacher training in gamification, monitoring and feedback on student progress, and applying the Mystery Box Game to enhance engagement and comprehension across multiple subjects.