This longitudinal study tested the same children at three time points: infancy (10.5months of age), toddlerhood (2.5years of age), and early childhood (4.5years of age). At 10.5months, infants were assessed experimentally with a gaze-following paradigm. At 2.5years, children’s language skills were measured using the MacArthur–Bates Communicative Development Inventories. At 4.5years, children’s explicit theory of mind was assessed with a standard test battery. Analyses revealed that infants with higher gaze-following scores at 10.5months produced significantly more mental-state words at 2.5years and that children with more mental-state words at 2.5years were more successful on the theory-of-mind battery at 4.5years. These predictive longitudinal relationships remained significant after controlling for general language, maternal education, and nonsocial attention. The results illuminate the bridging role that language plays in connecting infants’ social cognition to children’s later understanding of others’ mental states. The obtained specificity in the longitudinal relations informs theories concerning mechanisms of developmental change.