Electroencephalography (EEG), due to its peculiar time and spatial resolution, was used for the first time to fully monitor neuronal activation during the whole eye movement desensitization and reprocessing (EMDR) session, including the autobiographical script. The present case report describes the dominant cortical activations (Z-score >1.5) during the first EMDR session and in the last session after the client processed the index trauma. During the first EMDR session, prefrontal limbic cortex was essentially activated during script listening and during lateral eye movements in the desensitization phase of EMDR. In the last EMDR session, the prevalent electrical activity was recorded in temporal, parietal, and occipital cortical regions, with a clear leftward lateralization. These findings suggest a cognitive processing of the traumatic event following successful EMDR therapy and support evidence of distinct neurobiological patterns of brain activations during lateral eye movements in the desensitization phase of EMDR.