People quickly form impressions about moral character; for example, if people learn that someone cheated, they form a negative impression about that person's character and expect that person to cheat in the future. Four studies show that the formation of such moral character impressions depends on the degree of valence homogeneity in the target's context. We argue that this is the case because the degree of homogeneity in the context (the evaluative ecology) informs perceivers about the reliability of signals. Experiments 1 and 2 found that people form less strong impressions about moral character when a person's behavior occurred in a heterogeneous context, that is, if unrelated positive and negative context information cooccurred. Experiment 3 demonstrated that nonmoral valence homogeneity produces similar effects. In Experiment 4, this effect also influenced strategic decisions in economic games. Together, these studies demonstrate that evaluative ecology plays a critical role in shaping moral character impressions.