The construct validity of maternal mind-mindedness (MM) was investigated in the context of its relations with children's later understanding of mind. MM measures were obtained from infant–mother (N=52) interactions at 6 months, and from maternal interviews at 48 months. Children's understanding of mind was assessed using theory of mind (ToM) tasks at 45 and 48 months, and a stream of consciousness (SoC) task at 55 months. One of the early MM measures—mothers' appropriate mind-related comments—was a positive independent predictor of: (a) MM at 48 months, and (b) ToM and SoC performance at 45 to 55 months. Path analyses suggested direct links between mothers' use of appropriate mind-related comments and children's later understanding of mind.