Subjective memory and objective memory performance have predictive utility for clinically relevant outcomes in older adults. Previous research supports certain overlap between objective performance and subjective ratings of memory. These studies are typically cross-sectional or use baseline data only to predict subsequent change. The current study uses a parallel process model to examine concurrent changes in objective memory and subjective memory. We combined data from two population-based Swedish studies of individuals aged 80 + years, assessed every 2 years (OCTO—3 measurement occasions, OCTO-Twin—5 measurement occasions) yielding 607 participants (66% female). The results confirmed that both objective and subjective memory declined over time. The association between the slope of objective memory and subjective memory was statistically significant for women but not for men. This pattern remained after accounting for age and depressive symptoms. Our findings suggest that, in population-based samples of the oldest old, women seem to show better metacognitive abilities in detecting and reporting changes in memory. Memory changes for men may be better identified by objective performance as their self-assessment of memory changes is not associated with actual change in memory performance.