Children who are over-responsive to sensation have defensive and “fight or flight” reactions to ordinary levels of sensory stimulation in the environment. Based on clinical observations, sensory over-responsivity is hypothesized to reflect atypical neural integration of sensory input. To examine a possible underlying neural mechanism of the disorder, integration of simultaneous multisensory auditory and somatosensory stimulation was studied in twenty children with sensory over-responsivity (SOR) using event-related potentials (ERPs). Three types of sensory stimuli were presented and ERPs were recorded from thirty-two scalp electrodes while participants watched a silent cartoon: bilateral auditory clicks, right somatosensory median nerve electrical pulses, or both simultaneously. The paradigm was passive; no behavioral responses were required. To examine integration, responses to simultaneous multisensory auditory–somatosensory stimulation were compared to the sum of unisensory auditory plus unisensory somatosensory responses in four time-windows: (60–80ms, 80–110ms, 110–150ms, and 180–220ms). Specific midline and lateral electrode sites were examined over scalp regions where auditory–somatosensory integration was expected based on previous studies. Midline electrode sites (Fz, Cz, and Pz) showed significant integration during two time-windows: 60–80ms and 180–220ms. Significant integration was also found at contralateral electrode site (C3) for the time-window between 180 and 220ms. At ipsilateral electrode sites (C4 and CP6), no significant integration was found during any of the time-windows (i.e. the multisensory ERP was not significantly different from the summed unisensory ERP). These results demonstrate that MSI can be reliably measured in children with SOR and provide evidence that multisensory auditory–somatosensory input is integrated during both early and later stages of sensory information processing, mainly over fronto-central scalp regions.