The present study investigated changes in sulcal morphology associated with late-life aging and mild cognitive impairment (MCI). Participants were 219 community-dwelling 70–90 year-olds from the Sydney Memory and Ageing Study; all had MRI scans and were classified as having normal cognition (NC) or MCI at each of waves 1 and 2, two years apart. Automated methods were used to calculate a global sulcal index (g-SI), widths of five prominent sulci, and regional cortical thickness. There were significant longitudinal declines in g-SI and increases in sulcal width among the entire sample, but the rate of change differed among cognitive subgroups. Participants with MCI at both waves (persisting MCI) showed accelerated sulcal widening, particularly for the superior frontal and superior temporal sulci. The sulcal morphology of participants who reverted from MCI to NC was more consistent with stable NC than persisting MCI. Overall cortical thickness decreased between waves similarly across the subgroups. While changes in sulcal morphology are characteristic of normal late-life aging, they are accelerated in individuals with MCI (in contrast to changes in cortical thickness). Sulcal measures also differentiate between persistent MCI and MCI that reverts to NC, and may thus help in predicting the prognosis of MCI patients.