The aim of this study was to investigate the development of multisensory facilitation in primary school-age children under conditions of auditory noise. Motor reaction times and accuracy were recorded from 8-year-olds, 10-year-olds, and adults during auditory, visual, and audiovisual detection tasks. Auditory signal-to-noise ratios (SNRs) of 30-, 22-, 12-, and 9-dB across the different age groups were compared. Multisensory facilitation was greater in adults than in children, although performance for all age groups was affected by the presence of background noise. It is posited that changes in multisensory facilitation with increased auditory noise may be due to changes in attention bias.