In the recent literature in Artificial Intelligence, ethical issues are increasingly discussed. Many proposals of ethical agents are made. However, those approaches consider mainly an agent-centered perspective, letting aside the collective dimension of multi-agent systems. For instance, when considering cooperation among such agents, ethics could be a key issue to drive the interactions among the agents. This paper presents a model for ethics-based cooperation. Each agent uses an ethical judgment process to compute images of the other agents’ ethical behavior. Based on a rationalist and explicit approach, the judgment process distinguishes a theory of good, namely, how values and moral rules are defined, and a theory of right, namely, how a behavior is judged with respect to ethical principles. From these images of the other agents’ ethics, the judging agent computes trust used to cooperate with the judged agents. We illustrate these functionalities in an asset management scenario with a proof of concept implemented in the JaCaMo multi-agent platform.