It has been established that diabetes mellitus (DM) is a risk factor for dementia, and recent studies have clearly shown that dementia is one of the complications of DM. The increase of cognitively impaired subjects with the progression of aging in the population is an urgent worldwide issue. Due to the pharmacological advancement in the field of DM, we now have many kinds of antidiabetic medications with a wide variety of mechanisms of action and characteristics. It is a good time to review the characteristics of each antidiabetic medication and the evidence related to their prevention of cognitive dysfunction or preservation of cognition. The available data on the effects of antidiabetics on cognitive dysfunction and dementia show that several of the antidiabetics have the potential to improve cognition. The accumulation of more data to determine the best ways to use antidiabetics in order to prevent cognitive impairment would be warranted. To this end, the present review will try to illustrate the horizon of achievement in this field.