Aim The present prospective study used repeated measures analysis to identify potential Mini‐Mental State Examination (MMSE) score trajectories and determine whether MMSE trajectory was associated with incident disabling dementia among community‐dwelling older Japanese adults. Methods A total of 1724 non‐demented adults (mean age 71.4 years [SD 5.7]; 56.7% women) aged 65–90 years participated in annual geriatric health assessments during the period from June 2002 through July 2014. The total number of observations was 6755, and the average number of follow‐up assessments was 3.9. A review of municipal databases in the Japanese public long‐term care insurance system showed that 205 (11.9%) participants developed disabling dementia through December 2014. Results We identified three distinct MMSE score trajectory patterns (high, middle and low) in adults aged 65–90 years. After adjusting for important confounders, participants with middle (42.8%) and low (5.1%) MMSE trajectories had hazard ratios of 2.46 (95% confidence interval 1.64–3.68) and 10.73 (95% confidence interval 4.91–23.45), respectively, for incident disabling dementia, as compared with those in the high (52.1%) trajectory group. Conclusions Approximately half of the participants were classified as having a high MMSE trajectory, whereas 43% and 5% had middle and low MMSE trajectories, respectively, in this population. Individuals with middle and low MMSE trajectories had a higher risk for incident disabling dementia, which suggests that a high‐risk approach to dementia prevention should target people with mild and more rapid cognitive decline. Geriatr Gerontol Int 2017; ••: ••–••.