<p>Language forms the foundation of social interactions, allowing us to connect with family and peers. Through speech, we express our thoughts and emotions to others. Experiencing challenges in speech and language functions during development can therefore significantly affect social relationships, cognitive and affective development. In child and adolescence psychiatry, clinicians have observed that speech and language abilities may be altered in various mental (behavioral/developmental) disorders (psychiatric disorders). This review provides an overview of systematic and original investigations exploring how speech and language are affected in child and adolescent psychiatric conditions, including autism spectrum, schizophrenia, attention deficit/hyperactivity disorder, and depression. We emphasize research that utilized neuroimaging techniques (i.e., EEG, MRI, fNIRS) to investigate the neurobiological basis for alterations in speech or language in child and adolescence psychiatry. The findings indicate that each reviewed syndrome shows evidence of altered speech or language functions, along with corresponding neurobiological changes. Most available studies focus on autism spectrum, while research concerning schizophrenia and depression generally involved adults rather than children or adolescents. This highlights a considerable research gap in understanding (the neurobiological cause of) speech and language alterations in developing populations with psychiatric conditions.</p>