The relationship between mental models and ethical decision making, along with the mechanisms through which mental models affect EDM, are not well understood. Using the sensemaking approach to EDM, we empirically tested the relationship of mental models to EDM. Participants were asked to depict their mental models in response to an ethics case to reveal their understanding of the ethical dilemma, and then provide a response, along with a rationale, to a different ethical problem. Findings indicated that complexity of respondents’ mental models was related to EDM, and that this relationship was mediated by sensemaking processes. The implications of these findings for improving integrity training in organizations, as well as ultimately understanding the role of mental models in EDM, are discussed.