The human gut microbiome, which develops after birth and continues to evolve throughout life, plays a crucial role in early brain development and neurodevelopmental disorders (NDDs) in children. Factors such as mode of delivery, breastfeeding, antibiotic exposure, and maternal stress can alter the gut microbiome, which is interconnected with the brain via the gut-brain axis. This axis involves the nervous, endocrine, and immune systems and is involved in regulating brain development and function. Disruptions in the gut microbiome during early development may lead to neurodevelopmental disorders such as autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), Tourette syndrome, cerebral palsy, fetal alcohol spectrum disorders, and genetic NDDs like Rett, Down, Angelman, and Turner syndromes. The gut microbiome is influenced by factors such as mode of birth, feeding, and antibiotic use, with significant differences observed between vaginally delivered and cesarean-born infants. Breastfeeding promotes the growth of beneficial bacteria, while formula feeding leads to a different microbial composition. Early exposure to antibiotics reduces microbial diversity and stability, potentially increasing the risk of neurocognitive disorders. The transition to solid foods increases microbial alpha-diversity and pH, altering the dominant bacterial phyla. The gut microbiome influences brain development through mechanisms such as gene regulation, neuroactive molecule synthesis, and microglial activity. Microbial metabolites can affect epigenetic marks, gene expression, and neurotransmitter production, influencing brain plasticity and function. Changes in the gut microbiome have been associated with altered brain development and function in NDDs, with specific microbial taxa linked to symptoms in conditions like ASD and ADHD. In genetic NDDs such as Rett syndrome, Down syndrome, and Angelman syndrome, gut microbiome dysbiosis is associated with gastrointestinal disturbances and altered microbial composition. The gut microbiome's role in NDDs highlights the potential for future therapeutic interventions targeting the microbiome to improve outcomes in affected children.The human gut microbiome, which develops after birth and continues to evolve throughout life, plays a crucial role in early brain development and neurodevelopmental disorders (NDDs) in children. Factors such as mode of delivery, breastfeeding, antibiotic exposure, and maternal stress can alter the gut microbiome, which is interconnected with the brain via the gut-brain axis. This axis involves the nervous, endocrine, and immune systems and is involved in regulating brain development and function. Disruptions in the gut microbiome during early development may lead to neurodevelopmental disorders such as autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), Tourette syndrome, cerebral palsy, fetal alcohol spectrum disorders, and genetic NDDs like Rett, Down, Angelman, and Turner syndromes. The gut microbiome is influenced by factors such as mode of birth, feeding, and antibiotic use, with significant differences observed between vaginally delivered and cesarean-born infants. Breastfeeding promotes the growth of beneficial bacteria, while formula feeding leads to a different microbial composition. Early exposure to antibiotics reduces microbial diversity and stability, potentially increasing the risk of neurocognitive disorders. The transition to solid foods increases microbial alpha-diversity and pH, altering the dominant bacterial phyla. The gut microbiome influences brain development through mechanisms such as gene regulation, neuroactive molecule synthesis, and microglial activity. Microbial metabolites can affect epigenetic marks, gene expression, and neurotransmitter production, influencing brain plasticity and function. Changes in the gut microbiome have been associated with altered brain development and function in NDDs, with specific microbial taxa linked to symptoms in conditions like ASD and ADHD. In genetic NDDs such as Rett syndrome, Down syndrome, and Angelman syndrome, gut microbiome dysbiosis is associated with gastrointestinal disturbances and altered microbial composition. The gut microbiome's role in NDDs highlights the potential for future therapeutic interventions targeting the microbiome to improve outcomes in affected children.