This article explores the usefulness of a web-based education game for learning English idioms and examines attitudinal factors contributing to the learning of the idioms with the game. The two studies reported in this article involved two groups of English as a foreign language students in two different contexts. The students were surveyed on their opinions of language learning and games and tested on their idiom knowledge before and after using the web-based educational game over a similar period of gameplay time. The studies found that both groups had significant gains in idiom knowledge, with some variation. It was also found that idiom knowledge improvement was largely mediated by willingness to learn English. In addition, other factors such as satisfaction and self-perception of improvement were noted. It is suggested that, in game-based language learning, attitudinal and motivational factors such as satisfaction with games and willingness to learn with games need to be carefully considered as they can generate positive learning outcomes. Further studies on the use of online educational games for language learning are recommended to be conducted in and out of the classroom in line with the evaluation of the games.