Previous research has shown that the N1 responses are attenuated for sensory consequences of self-initiated actions compared to externally-initiated sensory consequences. This illustrates the existence of prediction mechanisms allowing the differentiation between self and externally generated events. Previous studies provided evidence for modulated N1 responses following self-initiated sounds or pictures. A recent study showed attenuated N1 responses also for self-initiated auditory-visual stimuli. The present study investigated the impact of temporal synchrony of the auditory and visual stimuli during self-initiated auditory-visual stimuli. To this end, different synchrony conditions were used: synchronous auditory-visual stimuli (Synced) and two asynchronous conditions with 100 ms delay between both stimuli, i.e. the auditory first followed by the visual stimulus (AV), and the vision first followed by the auditory stimulus (VA). These three conditions were recorded during an active task, which required the participant to push a button to trigger the presentation of the auditory-visual stimuli, and a passive task which was a replay of the formerly self-initiated auditory-visual stimuli. Attenuated N1 responses were observed for auditory-visual stimuli in the synced and auditory-first conditions. This highlights the role of auditory stimuli in modulating the size of the sensory attenuation effect for auditory-visual stimuli.