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Background: Distortion product otoacoustic emissions evaluate the function of outer hair cells in the cochlea. The present study aimed to compare distortion product otoacoustic emissions between normal hearing adult human and rat to better understand their differences. Materials and Methods: In this study, signal to noise ratio of distortion product otoacoustic emissions was evaluated and the results of normal hearing persons (n=60) and rats (n=30) were evaluated in similar conditions at of 2, 3, 4, and 5 KHz. Results: The difference between the two groups was significant in most frequencies except 3 KHz. In rats, a higher signal to noise ratio was observed at 4 and 5 KHz and a lower ratio at 2 KHz. There was no significant difference among different frequencies in human samples. Conclusion: Significant differences in distortion product otoacoustic emissions in the two groups may demonstrate the different mechanisms for cochlear function in human and rat. This result may indicate the need for extra cautions in using rats as an animal model.