The effective identification of neurodevelopmental disorders is essential for early diagnosis and provision of intervention services. For many of these conditions, one of the primary domains of abnormality is language development. This review addresses what is known about the earliest indicators of language impairment across a range of neurodevelopmental disorders; consideration is given to both behavioral and neural markers, as well as patterns of change over time. A summary of the current state of the field, including challenges in research, is presented. The earliest features of the language phenotype in Down syndrome, Williams syndrome, Fragile X, specific language impairment (SLI), and autism spectrum disorder (ASD) are described, along with recent findings in the early neural markers of language impairment in SLI and ASD. © 2013 Wiley Periodicals, Inc. Dev Disabil Res Rev 2011;17:151–159.