Koolen-de Vries Syndrome (KdVS), also referred to as 17q21.31 microdeletion syndrome, is caused by haploinsufficiency of theKANSL1gene. This genetic disorder is associated with a clinical phenotype including facial dysmorphism, developmental delay, and friendly disposition, as well as mild-to-moderate intellectual disability. We present the case of a 10 year 8 month old female with KdVS due to a de novo intragenicKANSL1mutation. At this time, she does not present with intellectual disability, and her verbal intelligence is relatively preserved, although she has perceptual deficits, developmental dyspraxia, and severe speech disorder. This case expands the mild end of the neurodevelopmental spectrum seen in children withde novo KANSL1mutation and KdVS.