—For students of English as a Foreign Language (EFL), vocabulary mastery is an essential component of language skills. Vocabulary may contribute to the success of language skills. However, most students had some trouble learning vocabulary. Vocabulary learning requires an advanced technology such as online game. Therefore, this paper aims to investigate the outcome of using an online game named SpellingCity to enrich vocabulary, which is a part of modern gamification. The research design is to have 22 students finish one turn game of SpellingCity and then fill out a survey and interview at the end of the data collection process. The result was that all students agree that using SpellingCity increase their vocabulary acquisition besides of also learning the pronunciation. SpellingCity simple interface design is also found to be one of the factors why SpellingCity considered interesting and easy to play by these students.