This study attempts to probe into the impact of learners' gender on learning outcomes and motivation. A digital game focusing on the topic of emergency first aid is designed for the purpose of this present study, according to the curriculum objectives for a content-based instruction (CBI) course as part of the experiment. In the process of playing the game, learners are able to acquire both first aid knowledge and language skills at the same time. Results show that gender has no significant effect on the learning achievement, but causes significant differences in learning motivation. Learners of different genders are found to have better learning achievement through digital game-based learning. In a moderate genre digital game, female learners' motivation is significantly higher than that of male learners. The usability of the digital game in this study receives positive response from learners regardless of gender. This evaluation on usability is correlated with the findings of this study. Our analysis also demonstrates that game contents in the moderate genre reduce the effect of gender on learning achievement and motivation. Based on the above findings, this study suggests a relationship between gender and digital game-based learning and proposes avenues for further research.