It has been reported that when a congruent natural sound precedes briefly presented visual stimuli, it promotes performance in psychophysics detection tasks. Onomatopoeias refer to words that phonetically mimic or suggest actual sounds. Onomatopoeic words are a form of sound symbolism and are frequently used in Japanese language. In this study, we examined whether the presentation of spoken Japanese onomatopoeia to Japanese native-speakers results in visual detection sensitivity changes. Results indicate that when onomatopoeias are presented 227 ms before a visual stimulus, they have a modulatory audiovisual effect. This effect is closer to the results observed with natural sounds than spoken words, with d' being lower for onomatopoeias when compared with natural sounds. Such suggests that Japanese spoken onomatopoeias may be processed in a manner that is closer to natural sounds than spoken words and points to behavioral consequences of sound symbolism.