© 2019 The Authors. Neuropsychopharmacology Reports published by John Wiley & Sons Australia, Ltd on behalf of the Japanese Society of Neuropsycho Pharmacology Aims: The brain function that detects deviations in the acoustic environment can be evaluated with mismatch negativity (MMN). MMN to sound duration deviance has recently drawn attention as a biomarker for schizophrenia. Nonhuman animals, including rats, also exhibit MMN-like potentials. Therefore, MMN research in nonhuman animals can help to clarify the neural mechanisms underlying MMN production. However, results from preclinical MMN studies on duration deviance have been conflicting. We investigated the effect of sound frequency on MMN-like potentials to duration deviance in rats. Methods: Event-related potentials were recorded from an electrode placed on the primary auditory cortex of free-moving rats using an oddball paradigm consisting of 50-ms duration tones (standards) and 150-ms duration tones (deviants) at a 500-ms stimulus onset asynchrony. The sound frequency was set to three conditions: 3, 12, and 50 kHz. Results: MMN-like potentials that depended on the short-term stimulus history of background regularity were only observed in the 12-kHz tone frequency condition. Conclusions: MMN-like potentials to duration deviance are subject to tone frequency of the oddball paradigm in rats, suggesting that rats have distinct sound duration recognition ability.