This continuation of a previous study (Taumoepeau & Ruffman, 2006) examined the longitudinal relation between maternal mental state talk to 15- and 24-month-olds and their later mental state language and emotion understanding (N= 74). The previous study found that maternal talk about the child’s desires to 15-month-old children uniquely predicted children’s mental state language and emotion task performance at 24 months. In the present study, at 24 months of age, mothers’ reference to others’ thoughts and knowledge was the most consistent predictor of children’s later mental state language at 33 months. Vygotsky’s zone of proximal development provides a framework within which maternal talk, first, about the child’s desires and then about others’ thoughts and knowledge scaffolds children’s social understanding.