The aim of this study was to test the hypothesis according to which theory of mind competence was a prerequisite to ambiguous idioms understanding. We hypothesized that the child needs to understand that the literal interpretation could be a false world representation, a false belief, and that the speaker's intention is to mean something else, to correctly process idiomatic expressions. Two kinds of ambiguous idioms were of interest: decomposable and nondecomposable expressions (Titone & Connine, 1999). An experiment was designed to assess the figurative developmental changes that occur with theory of mind competence. Five-, 6- and 7-year-old children performed five theory of mind tasks (an appearance–reality task, three false-belief tasks and a second-order false-belief task) and listened to decomposable and nondecomposable idiomatic expressions inserted in context, before performing a multiple choice task. Results indicated that only nondecomposable idiomatic expression was predicted from the theory of mind scores, and particularly from the second-order competences. Results are discussed with respect to theory of mind and verbal competences.