Game-based learning is important in helping teachers attract students’ interest in learning. Therefore, this study developed and investigated the usability of a game, namely Pirates Mathsdom, which was used to strengthen the students’ understanding of learning mathematics. The research design used is ADDIE model. A total of 30 pre-service mathematics teachers in Perak, Malaysia, were randomly selected. A questionnaire is developed to investigate the usability of Pirates Mathsdom and then analyzed using descriptive analysis and mean scores. Findings show that this game has a high validity and reliability value, with a Content Validity Index value of 1.00. Meanwhile, the level of usability is high, with the mean score values for each construct being 3.77 (design), 3.79 (ease of use), and 3.75 (satisfaction), respectively. The implication of the study is to promote games as one of the learning tools to attract students’ interest in mathematics.