We investigated the crossmodal temporal discrimination deficit characterizing older adults and its event-related potential (electroencephalogram) correlates using an audiovisual temporal order judgment task. Audiovisual stimuli were presented at stimulus onset asynchronies (SOA) of 70 or 270 ms. Older were less accurate than younger adults with an SOA of 270 ms but not 70 ms. With an SOA of 270 ms only, older adults had smaller posterior P1 and frontocentral N1 amplitudes for visual stimuli in auditory-visual trials and auditory stimuli in visual-auditory trials, respectively. These results suggest a deficit in cross-sensory processing with aging reflected at the behavioural and neural level, and suggest an impairment in switching between modalities even when the inputs are separated by long temporal intervals.