This study examines day-to-day variability in psychometrically defined mild cognitive impairment (MCI) status and potential predictors of changes in MCI status in an independent-living sample of urban dwelling older adults in Baltimore, Maryland. The participant sample consisted of 50 older adults, ranging in age from 50 to 80 years. Participants completed health and cognitive measures (i.e., executive function, language, memory, and global cognition) over 8 occasions within a 2–3-week period. After each testing occasion, a post hoc classification of MCI status was determined using psychometrically defined criteria based on cognitive performance. Participants who classified as MCI after one assessment often did not meet MCI criteria at subsequent occasions. Daily fluctuations in sleep duration were associated with an increased risk for MCI classification. These results demonstrate that changes in sleep may explain changes in MCI status, particularly for African Americans.