This study investigated the effects of a game-based instructional model on primary school pupils' achievement in arithmetic. 203 pupils from 6 classes in 6 schools participated. Pupils in the experimental group were taught arithmetic using games, while the control group used conventional methods. Pupils completed a pre-test and post-test on arithmetic skills. Results showed the experimental group significantly outperformed the control group on the post-test. Additionally, female pupils in the experimental group scored higher on average than male pupils, though both benefited from the game-based approach. The study concluded game-based instruction is an effective way to improve pupils' arithmetic learning and performance.