Previous studies have suggested sentential complementation is the crucial ingredient of languagethat relates to false-belief (FB) reasoning, while the role of relative clauses (RCs) is less clear.Nevertheless, under the hypothesis that clausal embedding has a meta-representational effect,arguably implied in FB, one expects a link between FB and not only complementation but alsorelativization. Seventeen children with ASD (6 to 16 years, mean age 9;2) were assessed for RCsand FB. Comprehension of RCs significantly predicted FB performance, while none of the con-trolled factors played a predictive role (comprehension of simple sentences, vocabulary, morpho-syntax and working memory). Findings suggest that clausal embedding, common to both sen-tential complements and RCs, serves as a bootstrap for FB reasoning.