Our ability to merge information from different senses into a unified percept is a crucial perceptual process for efficient interaction with our multisensory environment. Yet, the developmental process underlying how the brain implements multisensory integration remains poorly known. This cross-sectional study aims to characterize the developmental patterns of audiovisual events in 131 individuals aged 3 months to 30 years. Electroencephalography (EEG) was recorded during a passive task, including audiovisual, auditory, and visual stimulations. Different developmental patterns are seen for the audiovisual, auditory, and visual responses, with the visual and audiovisual responses reaching maturity between 11 and 14 years old and the auditory response reaching maturity a few years later, between 15 and 17 years old. Topographic distributions reveal distinct audiovisual developmental patterns across age groups. Specifically, from 3 months to 7 years old, audiovisual interaction emerges in the left temporo-parietal regions and reaches the medial frontal area between 8 and 10 years old, followed by a mature fronto-central pattern from 11 years old. Our results show that response to the bimodal events is a long developmental process that emerges during childhood and continues to develop during adolescence.