Cognitive complaints and engagement in cognitive activities are two consistent predictors of cognitive aging outcomes, including risk for nonnormative decline. Though research has considered predictors of complaints and engagement in general, little work has attended to the fact that these fluctuate at the daily level. The current study examined individual difference predictors of means and variability for engagement and complaints across 10 days in a sample of older adults (n = 136; Mage = 70.45 years). When comparing personality traits to indicators of cognitive performance, personality differences appeared better unique predictors for these measures of daily cognitive life. Specifically, even when accounting for demographics, measures of cognitive performance, and the other personality traits investigated, older adults higher on openness to experience reported fewer daily cognitive complaints and more engagement on average, as well as greater daily variability in engagement. In addition, higher neuroticism predicted greater variability in reports of cognitive complaints across days. Implications are discussed with respect to how these findings advance our understanding of cognitive complaints and engagement in daily life. (PsycInfo Database Record (c) 2020 APA, all rights reserved).