The Theory of Mind Inventory is an informant measure designed to evaluate children's theory of mind competence. We describe the translation and cultural adaptation of the inventory by the following process: (1) translation from English to Spanish by two independent certified translators; (2) production of an agreed version by a multidisciplinary committee of experts; (3) back-translation to English of the agreed version by an independent translator; (4) discussion of the semantic, idiomatic, and cultural equivalence of the final version; (5) elaboration of the final test; (6) pilot test on 24 representatives of the autism spectrum disorders population and 24 representatives of typically developing children. The steps were conducted satisfactorily, producing the final version in Spanish, which showed good psychometric properties.