**Objectives**: Dispersion in cognitive test performance within a single testing session is proposed as an early marker of poor brain health. However, little is known about factors that may explain individual differences in cognitive dispersion. Given that individual differences in personality traits are associated with cognitive performance, we investigate the extent to which the Big Five Personality traits are also associated with cognitive dispersion in older adulthood. **Method**: To promote transparency and reliability, we applied pre-registration and conceptual replication via coordinated analysis. Drawing data from seven, diverse longitudinal studies of aging (Ntotal=33,581; Mage range=56.4-71.2), cognitive dispersion scores were derived from cognitive test results. Independent linear regression models were fit in each study to examine personality traits as predictors of dispersion scores, adjusting for mean cognitive performance and socio-demographics (age, sex, education). Results from individual studies were synthesized using random effects meta-analyses. **Results**: Results revealed minimal evidence for associations between cognitive dispersion and personality traits in independent analyses or in meta-analyses. Openness was the only statistically significant meta-analytic estimate (0.028, 95%CI:[0.003,0. 054]). Mean cognitive scores were negatively associated with cognitive dispersion across the majority of studies; socio-demographic variables, however, were not consistently associated with cognitive dispersion across studies. **Discussion**: Higher levels of openness were associated with greater cognitive dispersion across seven independent samples. Further research is needed to investigate mechanisms that may help to explain the link between openness and cognitive dispersion, as well as to identify additional individual factors, beyond personality traits, that may be associated with cognitive dispersion.