Abstract Objective An analysis of EEG synchrony between homologous early visual areas tested the hypothesis that interhemispheric functional connectivity during visual stimulation is reduced in children with autism compared to controls. Methods EEG power and coherence within and between two homologous regions of the occipital cortex were measured during long latency flash visual evoked potentials. Measures were compared between two groups of children (5.5–8.5 years), one with autism spectrum disorders and the other with typical development. Results In and below the theta band, interhemispheric synchrony was reduced in autistic subjects compared to typical controls by as much as 50%. Above the theta band interhemispheric synchrony in autistic children became indistinguishable from what would occur for uncorrelated cortical activity. Interhemispheric synchrony in autistic subjects was decreased in spite of bilaterally increased power. Wavelet power showed autistic children had a more rapid initial response to stimulation, a slower recovery, and more modulation at longer latencies. Conclusions Results suggest that the sensory cortices of autistic children are hypersensitive to stimulation with concurrent diminished functional connectivity between hemispheres. Significance Simultaneously increased intrahemispheric power and decreased interhemispheric synchronization of elemental visual information suggests either that power increases cause poor interhemispheric connectivity or that processes, such as thalamocortical regulation, impact power and coherence independently.