Language and communication skills are essential aspects of child development, which are often disrupted in children with neurodevelopmental disorders. Cutting edge research in psycholinguistics suggests that multilingualism has potential to influence social, linguistic and cognitive development. Thus, multilingualism has implications for clinical assessment, diagnostic formulation, intervention and support offered to families. We present a systematic review and synthesis of the effects of multilingualism for children with neurodevelopmental disorders and discuss clinical implications.We conducted systematic searches for studies on multilingualism in neurodevelopmental disorders. Keywords for neurodevelopmental disorders were based on Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition categories as follows; Intellectual Disabilities, Communication Disorders, Autism Spectrum Disorder (ASD), Attention-Deficit/Hyperactivity Disorder, Specific Learning Disorder, Motor Disorders, Other Neurodevelopmental Disorders. We included only studies based on empirical research and published in peer-reviewed journals.Fifty studies met inclusion criteria. Thirty-eight studies explored multilingualism in Communication Disorders, 10 in ASD and two in Intellectual Disability. No studies on multilingualism in Specific Learning Disorder or Motor Disorders were identified. Studies which found a disadvantage for multilingual children with neurodevelopmental disorders were rare, and there appears little reason to assume that multilingualism has negative effects on various aspects of functioning across a range of conditions. In fact, when considering only those studies which have compared a multilingual group with developmental disorders to a monolingual group with similar disorders, the findings consistently show no adverse effects on language development or other aspects of functioning. In the case of ASD, a positive effect on communication and social functioning has been observed.There is little evidence to support the widely held view that multilingual exposure is detrimental to the linguistic or social development of individuals with neurodevelopmental disorders. However, we also note that the available pool of studies is small and the number of methodologically high quality studies is relatively low. We discuss implications of multilingualism for clinical management of neurodevelopmental disorders, and discuss possible directions for future research.