Many beliefs about oneself are constructed through experience, but the kinds of evidence that inform these beliefs in early childhood are not well understood. One source of information that affects adults and older children’s appraisals of themselves is social comparison. We found that even preschoolers (mean=57 months) spontaneously use social comparisons to guide their behavior. In Experiment 1, children who saw they out-performed peers on a task subsequently persisted less than children in other conditions. Children who saw evidence suggesting they performed either better or worse than peers on the task were more likely to choose an easy (versus difficult) novel task relative to those who saw neutral or no evidence. In Experiment 2 children who saw peers perform better were inclined to persist more than children in other conditions. This suggests preschoolers use social comparison to draw inferences about themselves without explicit cues, and this affects their motivation.