Theater has emerged as a dynamic, participatory, and effective tool for addressing complex social and health-related issues in a culturally sensitive and tailored manner. Its ability to create emotionally immersive experiences and foster meaningful interactions between audience members and actors makes it uniquely suited for promoting health and well-being, especially when co-created with the target population. This chapter explores some theoretical underpinnings of theater-based interventions for health promotion: social cognitive theory, which emphasizes the role of observational learning and self-efficacy; the health belief model, which focuses on perceived susceptibility, severity, and perceived outcome expectations; and the theory of planned behavior, which highlights the importance of attitudes, subjective norms, and perceived behavioral control in predicting intentions and behavior. Further, different approaches to applied theater and its effects are discussed, with a specific focus on participatory forms: Participatory theater involves audience members in the creation and performance of the play, while forum theater allows for interactive dialogue and exploration of different perspectives with the audience. The chapter ends with a brief review of theater-based interventions among diverse populations, including youth, older adults, and healthcare professionals, and it highlights the most often targeted health issues, including sexual and reproductive health and HIV/AIDS, substance abuse, mental health, and chronic diseases. The chapter concludes that theater offers a promising approach to health promotion but that several methodological limitations prevent an estimation of its true impact on (changing) health behavior.