Vocabulary acquisition is a key factor in improving English proficiency among young learners. Due to the difficulties students often experience in memorizing and effectively using vocabulary, this study applied a game-based learning strategy. The Treasure Hunt Game, conducted outdoors, encourages student engagement through collaborative tasks, mission completion, exploration of surroundings, and reward mechanisms, reflecting the principles of experiential learning.

This research utilized a quasi-experimental design with a quantitative approach, involving two groups: an experimental group and a control group. The participants were third-grade students at SD Islam Darush Sholihin Nganjuk, selected through purposive sampling. Each group consisted of 20 students, making a total of 40 participants in the study. The control group (Class 3A) was taught using the conventional guessing game method, whereas the experimental group (Class 3B) engaged in the Treasure Hunt Game. Pre-tests and post-tests were administered to evaluate vocabulary mastery before and after the intervention.

The primary objective was to assess the effectiveness of the Treasure Hunt Game in enhancing vocabulary mastery and to determine whether significant differences exist when compared to traditional teaching methods. Data analysis, conducted using SPSS version 27 with an independent samples t-test, indicated a significant improvement in the experimental group. The p-value obtained was 0.000, which is below the 0.05 significance threshold, leading to the acceptance of the alternative hypothesis (Ha) and the rejection of the null hypothesis (H0).

The results suggest that the Treasure Hunt Game is a highly effective and engaging instructional method for improving vocabulary mastery among young learners, offering a valuable alternative to conventional approaches.

Keywords: Effectiveness, Treasure Hunt Game, EYL, Vocabulary Mastery, Game-Based Learning, Outdoor Learning