This study's objectives were to develop the English vocabulary manual for football enthusiasts, evaluate the characteristics, qualities, and usability factors contributing to users' satisfaction with the developed manual, and investigate its effectiveness in improving their football skills and overall performance on the field. The data was collected from 40 participants, divided into two groups: 20 undergraduate students and 20 football enthusiasts, employing the Wilcoxon Signed-Rank Test quantitative analysis and a theme-based qualitative analysis. Responses were initially gathered in Thai and subsequently translated into English. Findings indicate that the manual significantly enhanced users' understanding of football terminology, influencing their confidence and gameplay. Users particularly appreciated the manual's comprehensive coverage, categorised into Apparel, Gameplay, Judging, and Positions. Besides, users reported noticeable overall performance and communication improvements during football matches. When juxtaposed with existing literature, the results resonate with previous studies on specialised language acquisition and sports education. The study concludes that the vocabulary manual is a valuable resource for learners and football enthusiasts, meeting and often exceeding expectations in its usability and effectiveness. Recommendations for pedagogical implementations and avenues for further research are discussed.