Affective and cognitive Theory of Mind (ToM) is known to be deficit or delayed in children with intellectual disabilities (IDs), when compared with typically developing children matched for developmental age. Yet, little is known about causal contribution of affective and cognitive ToM on emotion regulation or social adjustment in these children. Studies that aimed to answer this problematic, implemented training focusing on the nine mental states -mainly on beliefs and emotions -and in toddlers and adolescents' samples, rarely compared to control group. The present study aims at testing whether training ToM abilities notably affective and cognitive mental states in children with IDs could foster ToM, but also their emotion regulation and social adjustment. 30 children with mild or moderate IDs functioning at preschool developmental age, took part in a pre-test session involving measures on cognition and ToM. Teachers and/or parents completed questionnaires evaluating children's emotion regulation and social adjustment. Secondly, children were allocated to control or experimental group which benefits from the specific "ToM program for children". It was delivered in eight sessions, by an experimented searcher to sub-groups of three children. Finally, all children took part in a post-test session. Results showed significant improvement of affective and cognitive ToM abilities in children with IDs in experimental groups. After ToM training, they displayed a better understanding of cognitive mental states and of consequences of emotions. In post-tests, they are perceived as more socially adjusted by teachers.