AbstractObjectivesTo delineate midlife personality dimensions of early cognitive change in an age‐homogenous sample of U.S. older adults.DesignLongitudinal study of 6133 adults from the Wisconsin Longitudinal Study (WLS).MeasuresMiddle‐aged participants (mean age = 53.2; SD = 0.6) from the WLS completed the ‘Big‐5’ personality assessment in 1992. Mixed effects models examined whether midlife personality traits were associated with change in cognitive performance from participant's mid‐60s (2004–2005) to early 70s (2011). The cognitive battery assessed abstract reasoning (AR), category fluency (CF), working memory (WM), and delayed verbal memory (DVM). Models adjusted for sex, education, and subjective health.ResultsHigh Openness was a significant predictor of change in AR, CF, and DVM. These cognitive outcomes declined less among those with high Openness, but the effect sizes for Openness by time were small (R²s < 0.01). AR and CF were characterized by higher overall performance with high Openness, but with relatively parallel change for the highest and lowest Openness quartiles. There was no advantage of Openness to DVM by the second assessment. High Conscientiousness was a predictor of more change for DVM, though the effect size was small (R ² < 0.01).ConclusionsNone of the midlife personality traits were uniformly associated with change in cognitive performance in early older adulthood. High midlife Openness had the most noteworthy impact on cognition. Interventions designed to target Openness have potential to elevate and maintain a higher threshold of performance in some cognitive domains, but may only have a small impact on cognitive change.