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The current investigation examined intraindividual variability and predictors of this variability on neuropsychological measures. A total of 50 (39 women and 11 men) independently living, community-dwelling African Americans ranging in age from 50 to 80 years (M = 65.40, SD = 8.53) were asked to complete measures assessing socio-demographics, physical health (i.e. blood pressure and sleep), and cognitive functioning (i.e. executive function, memory, perceptual speed, constructions, and language) over 8 occasions within a 2-3 week period. The current study observed intraindividual variability across the neuropsychological measures. Results from multilevel modeling suggested that a within-person change in systolic blood pressure was positively associated with performance on executive function (e.g., Letter Fluency), particularly for those participants who on average had high systolic blood pressure and high stress. In contrast, a within-person change in sleep duration was associated with worse performance on constructions and executive functioning (e.g., Letter Fluency). Results also reflected a significant interaction between within-person change in sleep duration and average sleep duration for both perceptual speed (e.g., Number Comparison test) and executive function (e.g., Stroop task). Individuals with low sleep duration on average tended to perform poorly, particularly on those occasions when their sleep duration was below their personal average. In contrast, individuals with high sleep duration on average tended to perform poorly, particularly on those occasions when their sleep duration was above their personal average. Furthermore, daily fluctuations in sleep duration were associated with an increased risk for classification of mild cognitive impairment. The results suggest that variability on neuropsychological measures may be a useful clinical assessment of older African Americans’ cognitive competency.