This study examines the contribution of children's linguistic ability and mothers' use of mental-state language to young children's understanding of false belief and their subsequent ability to make belief-based emotion attributions. In Experiment 1, children (N = 51) were given three belief-based emotion-attribution tasks. A standard task in which the protagonist was a story character and the emotional outcomes were imagined, and two videos in which the story protagonist was a real infant and the emotional outcomes were observable (high and low expressed emotion conditions). Children's verbal ability (semantic competence) was also measured. In Experiment 2, children (N = 75) were given two belief-based emotion tasks: the standard story task and the high expressed emotion video. In addition, children's verbal ability (syntactic competence) and mothers' use of mental-state attributes when describing their children were also measured. The results showed that: (1) the lag between understanding false belief and emotion attribution was a stable feature of children's reasoning across the three tests; and (2) children who were more linguistically advanced and whose mothers' described them in more mentalistic terms were more likely to understand the association between false belief and emotion. The findings underline the continuing importance of verbal ability and linguistic input for children's developing theory-of-mind understanding, even after they display an understanding of false belief.