Young children have problems reasoning about false beliefs. We suggest that this is at least partially the result of the same curse of knowledge that has been observed in adults—a tendency to be biased by one's own knowledge when assessing the knowledge of a more naive person. We tested 3- to 5-year-old children in a knowledge-attribution task and found that young children exhibited a curse-of-knowledge bias to a greater extent than older children, a finding that is consistent with their greater difficulty with false-belief tasks. We also found that children's misattributions were asymmetric. They were limited to cases in which the children were more knowledgeable than the other person; misattributions did not occur when the children were more ignorant than the other person. This suggests that their difficulty is better characterized by the curse of knowledge than by more general egocentrism or rationality accounts.