The hypothesis that language plays a role in theory-of-mind (ToM) development is supported by a number of lines of evidence (e.g., H. Lohmann & M. Tomasello, 2003). The current study sought to further investigate the relations between maternal language input, memory for false sentential complements, cognitive flexibility, and the development of explicit false belief understanding in 91 English-speaking typically developing children (M age = 61.3 months) and 30 children with specific language impairment (M age = 63.0 months). Concurrent and longitudinal findings converge in supporting a model in which maternal language input predicts the child's memory for false complements, which predicts cognitive flexibility, which in turn predicts explicit false belief understanding.