OBJECTIVE: This study examined the joint roles of dispositional optimism and Big-Five personality factors in preserving "Not-Impaired-Not-Demented" status, assessed four times biennially over an eight-year period, among older Black Americans born before 1964. Mediation by biomarkers (e.g., Cystatin C, C-reactive protein, blood sugar, lipids, BMI, blood pressure), assessed twice quadrennially, was also tested to confirm possible facilitation of homeostasis by these traits. DATA AND METHODS: Data were obtained from 3,229 Black participants in the Health and Retirement Study, all aged 50 or older at baseline and born before 1964. A latent growth curve model was employed to model the log-odds of being "Not-Impaired-Not-Demented" over the eight-year period with optimism and the Big-Five factors. RESULTS: Optimism was associated with higher initial odds of maintaining "Not-Impaired-Not-Demented" status, independent of negative psychological factors (e.g., depression, discrimination). There was no evidence of mediation through biomarkers. Extraversion further increased the odds when optimism was above average, while neuroticism decreased them. Agreeableness independently contributed to higher odds, regardless of optimism levels. CONCLUSION: Future research may further explore if the co-development of optimism and assertive/purposeful social interactions coalesces to benefit working memory in advanced age specifically for this cohort of older Black Americans.