Autism spectrum disorder (ASD) is a severe neurodevelopmental disorder with a rising prevalence and genetic and environmental etiologies. Symptoms include deficits in social communication, repetitive patterns of behavior, and cognitive impairment. Neuroanatomic and biochemical investigations involve many brain areas with imbalance between glutamatergic and inhibitory neurotransmitters. We hypothesized that investigation of the synaptic compartment of the dorsolateral prefrontal cortex may provide proteomics signatures that may identify the biological underpinnings of cognitive deficits in childhood ASD. Subcellular fractionation of the synaptoneurosomes from Brodmann area 9 of a well- characterized age- and postmortem-interval-matched samples from children and adults with idiopathic ASD vs. healthy controls, were subjected to HPLC–tandem mass spectrometry and proteomic analysis.