Disaster prevention is a critical issue in Japan, requiring proactive citizen education, effective disaster notifications, and accessible evacuation routes. However, citizen engagement in disaster prevention activities and tools remains relatively low. Traditional methods, such as disaster drills, often struggle to maintain long-term interest among citizens. Capitalizing on the increasing popularity of hobbyist digital game development, this paper proposes using a serious game jam—a collaborative game creation event—for disaster education and awareness raising. Based on data from a serious game jam organized in spring 2024, the paper evaluates the effects of participation on respondents’ awareness, knowledge, and feelings relating to disaster prevention. The findings suggest the game jam was effective in terms of increasing participants’ conceptual understanding, including one month after the event, but did not have a significant emotional or motivational effect. The paper discusses how to remedy this, as well as improve longer-term retention.