Purpose: The main aim of the paper is to explore whether health theatre as a school-based health promotion initiative communicates relevant health knowledge to children and the interrelated processes of identity development, knowledge acquisition and participation. Development of the definition of "health identity" was a subsidiary objective of the study. Design/methodology/approach: This was a qualitative study based on observation of five health theatre performances, with 20 focus group interviews with a total of 98 children and 22 individual interviews with teachers and parents. Findings: Three themes emerged from the qualitative analysis: children's varying capacities for participation affect knowledge acquisition and identity development; health knowledge acquisition is enhanced when information is made relevant by linking health to everyday life; and acquisition of health information and children's health identities are closely related. Coherent information and environments are conducive to knowledge acquisition, and health promotion efforts must be careful to avoid reinforcing negative health identities and furthering perceived divisions between "healthy" and "unhealthy" children. Originality/value: The paper provides important foundational information for school-based health theatre initiatives. It presents knowledge for practitioners working with knowledge-based health promotion for children and explores the connection between identities, health knowledge acquisition and participation within an alternative theoretical framework.