The Twelfth International Conference on Human-Agent Interaction (HAI 2024) aims to be the premier interdisciplinary venue for discussing and disseminating state-of-the-art research and results that have implications across conventional interaction boundaries including robots, software agents and digitally-mediated human-human communication. HAI will gather researchers from fields spanning engineering, computer science, psychology and sociology, and will cover diverse topics, including: human-robot interaction, affective computing, computer-supported collaborative work, gaming and serious games, artificial intelligence, and more.