Individuals with diabetes can develop cognitive impairment due to dysfunction of glucose metabolism; however, it remains unclear whether cognition becomes altered in the prediabetic stage. Substantial evidence links cognitive impairment in diabetes to aberrant serum insulin-degrading enzyme (s[IDE]) levels. This relationship remains to be investigated in individuals with prediabetes.To investigate the relationship between cognitive function and s[IDE] levels in individuals with prediabetes.The study group consisted of 47 individuals who had been diagnosed with prediabetes and 41 healthy controls. Cognitive functions were evaluated using the Montreal Cognitive Assessment (MoCA), and s[IDE] levels were measured using enzyme-linked immunosorbent assay.The MoCA total scores and s[IDE] levels of the individuals with prediabetes were significantly lower (P = 0.001, 0.006) than those of the controls, and the MoCA Attention measure of the individuals with prediabetes was also very low (P = 0.001). To determine cognitive impairment, we divided the prediabetics into two subgroups according to the MoCA cutoff value. Scores on all of the MoCA tests were significantly lower in the group with mild cognitive impairment (P < 0.05). There was no correlation between MoCA scores and s[IDE] levels (P > 0.05), but serum-fasting glucose levels showed a negative correlation with MoCA scores (P < 0.05, ρ = -0.287).Evidence of mild cognitive impairment was high in the individuals with prediabetes and showed a negative correlation with serum-fasting glucose levels but not with s[IDE] levels.