This study investigates the impact of traditional versus game-based teaching methods on young learners’ acquisition and retention of English vocabulary. The research was conducted as a small-scale classroom experiment with two groups of Swedish primary school students. One group received vocabulary instruction through traditional methods, while the other was taught using game-based activities. Pre-tests, post-tests, and a delayed post-test were used to measure and compare students’ vocabulary learning outcomes over time. The results showed that both instructional approaches led to improved vocabulary knowledge. Students in the traditional group demonstrated greater gains in the immediate-post-test, suggesting that structured and repetitive exercises may support short-term acquisition. Although students in the game-based group showed smaller initial improvements, however, they exhibited continued progress in the delayed post-test, indicating potential benefits for long-term retention. These findings suggest that while traditional instruction may be effective for short-term vocabulary gains, game-based activities can support long-term retention of vocabulary among young learners.