The role of event knowledge in early language acquisition was investigated. Thirteen two-year-olds were observed interacting with their mothers over a five-week period. During weekly observational sessions, dyads interacted in both a familiar-event context and an unfamiliar-event context. Events were represented by complex toys (e.g. airport, marina, etc.). In the familiar-event, dyads interacted with the same event-toy during each observation period. In the unfamiliar-event, these same dyads interacted with a different novel toy during each observation period. The results indicated that children's increasing event knowledge facilitated their language development. Specifically, children's lexical type use, action verb use, and MLU increased in the familiar-event, but remained unchanged in the unfamiliar-event. Event knowledge also facilitated children's lexical token use. Results are discussed in terms of the role of event knowledge in language acquisition.