A growing number of studies have been conducted on digital game-based learning (DGBL). However, there has been a lack of attention paid to individuals' self-efficacy and learning performance in the implementation of DGBL. This study therefore investigated how the badge mechanism in DGBL enhanced users' self-efficacy in the subject domain of English as a foreign language. In the study, a digital game-based English learning environment was designed with a badge mechanism including digital badges, leaderboard ranking, and learning practice with star icons. A quasi-experimental design was implemented. A total of 50 third-grade elementary school students participated in this study. Hypotheses were tested, and data were analyzed using paired sample "t" tests, multiple regression analyses, linear regression analyses, and logistic regression analyses. The results show that the badge mechanism had a significant positive influence on the learners' self-efficacy and English learning performance. The study also investigated how self-efficacy could affect English learning performance, with the results revealing that it had a significant positive influence on learning performance. In addition, a subsequent analysis showed that those students with higher self-efficacy performed better than those with lower self-efficacy.