This paper summarizes the results of 11 separate studies of deaf children’s performance on standard tests of false belief understanding, the results of which combine to show that deaf children from hearing families are likely to be delayed in acquiring a theory of mind. Indeed, these children generally perform no better than autistic individuals of similar mental age. Conversational and neurological explanations for deficits in mental state understanding are considered in relation to recent evidence from studies of deaf, autistic, and normally developing children with varied levels of access to talk about mental states at home with family members during the preschool years.