Combining information across modalities can affect sensory performance. Here we studied how auditory stimuli modulate behavioral performance to visual stimulus detection of higher or lower contrast and its temporal dynamics with event related potential (ERP) and event related magnetic fields (ERMF). We varied the contrast of visual stimuli (gabor gratings) and orthogonally the presence of a sound while subject perform a visual detection task and ignored any co-occurring sounds, that yielded no information about stimulus occurrence. Behaviorally, we found significantly higher detection performance for low intensity stimuli paired with sound, reflected by hit rate and d-prime, but no changes for high intensity stimuli paired with sound. Importantly, no change in response criterion (ß) could be observed suggesting that our finding reflects a ‘true’ enhancement of sensitivity. The ERPs/ERMFs grand-average signatures indicate that this multisensory integration process for low intensity stimuli is associated with early neural activations over parieto-occipital sensors/electrodes. Our results indicate that this sound-induced visual contrast enhancement is associated with an early modulation of processing in putative unisensory cortex.