In adult, a salient tone embedded in a sequence of non-salient tones improves detection of a synchronously presented brief visual target in rapid visual distracting sequence (Vroomen & de Gelder 2000). Wada et al., (2009) reported that audio-visual enhancement in visual detection is emerged at 7 month of age using illusory-contours composed of 4 packmen as visual target. However, it is still unclear whether the finding would be related to the multisensory perceptual organization or that would reflect the development of attention. Here, we examined these issues with 2 experiments. We used a preferential looking technique to investigate whether audio–visual enhancement of the detection of visual target could be observed at 5, 6, and 7 months of age. In the first experiment, we used a non-illusory target: each packman kept their back to the others. In the second experiment the salient sound was presented together with the distractor just before the target illusory-contour figure. Results indicated that the preference for targets was significant only in 7-month-olds in the first experiment. No audio-visual enhancement was observed in the second experiment. These results confirm the audio–visual enhancement in visual target detection emerges as multisensory organization at 7 months of age.