Recent studies have shown that simulation games may be useful tools for supporting foreign language education. However, much of this research has focused on games using 3D graphic technology, which entail technical requirements that may render them too complex for use in many educational contexts. Accordingly, we wanted to determine if less complex simulation games could also support the acquisition of a foreign language. We conducted a quasi-experiment using whole classes comprising EFL learners at a Japanese university. A treatment group used an online vocabulary learning application (Quizlet) in conjunction with a simple simulation game (3rd World Farmer), and a control group used the vocabulary learning application alone. Although using the simulation game showed no short-term benefit, the treatment group outperformed the control group on a delayed post-test administered 11 weeks after treatment. We conclude that the effect of simulation games can be used in foreign language learning to improve long-term retention of target language vocabulary.