Tattling, defined as the reporting to a second party of norm violations committed by a third party, is a frequent but little-studied activity among young children. Participant observation and quantitative sampling are used to provide a detailed characterization of tattling in 2 preschools (initial mean age = 4.08 years, = 40). In these populations, tattling represents the majority of talk about peers’ behavior to third parties. It is usually truthful, it rarely refers to transgressions committed against other individuals, it is not often ignored by adults, it is performed more frequently by dominant children, and it correlates with teacher reports of relational aggression. These exploratory results suggest several new avenues of research into children’s developing understanding of social norms.