INTRODUCTION: Midlife hypertension is a well-established predictor of late-life cognitive decline; however, few population-representative estimates of this association exist among oldest-old cohorts. METHODS: LifeAfter90 (LA90) is an ethnoracially diverse cohort of individuals aged 90+ linked to midlife multiphasic health check-ups (MHC). We assessed executive function, semantic memory, and verbal memory at age 90+. We used stabilized inverse probability of censoring weights and linear regression to estimate the association between midlife hypertension and cognitive function in the MHC target population. RESULTS: After weighting, LA90 participants (n = 307) were similar to the MHC population on race/ethnicity, hypertension, and education. Midlife hypertension was not associated with executive function (β = 0.03, [95% confidence interval [CI]: -0.24, 0.31]) and verbal memory (β = -0.10 [95% CI: -0.37, 0.16]). Midlife hypertension was associated with poorer semantic memory (β = -0.19 [95% CI: -0.44, 0.06]). DISCUSSION: People with midlife hypertension averaged lower semantic memory using population-representative models, suggesting that it may have sustained impact on learning and memory in those aged 90+.