Three experiments (total N = 140) tested the hypothesis that 5-year-old children’s membership in randomly assigned “minimal” groups would be sufficient to induce intergroup bias. Children were randomly assigned to groups and engaged in tasks involving judgments of unfamiliar in-group or out-group children. Despite an absence of information regarding the relative status of groups or any competitive context, in-group preferences were observed on explicit and implicit measures of attitude and resource allocation (Experiment 1), behavioral attribution, and expectations of reciprocity, with preferences persisting when groups were not described via a noun label (Experiment 2). In addition, children systematically distorted incoming information by preferentially encoding positive information about in-group members (Experiment 3). Implications for the developmental origins of intergroup bias are discussed.