The Perceptions of Children's Theory of Mind Measure (Experimental version; PCToMM-E) is an informant measure designed to tap children's theory of mind competence. Study one evaluated the measure when completed by primary caregivers of children with autism spectrum disorder. Scores demonstrated high test-retest reliability and correlated with verbal mental age and ToM task battery performance. No ceiling effects were observed. In addition, caregivers accurately predicted their children's ToM task battery performance. In study two the scores of primary caregivers of typically developing children demonstrated high test-retest reliability and distinguished children on the basis of age and developmental status. Ceiling effects were not evident until late childhood. The utility of the PCToMM-E and directions for future research are discussed.