Accurate self-assessment of memory is important for everyday function. Self-rating accuracy may be affected by several factors in aging, and especially in Parkinson’s disease (PD), but these putative influences have rarely been examined in the same study to determine their relative importance and the potential interactions among them. We examined self-ratings of memory in healthy older adults and people with PD. We used two metamemory scales: the relatively comprehensive Multifactorial Memory Questionnaire (MMQ) and the more brief Structured Telephone Interview for Dementia Assessment (STIDA). We took into account three key influencing variables: depression, personality variables (especially neuroticism and conscientiousness), and executive functions. The MMQ ability scale and the STIDA were moderately correlated for controls whereas this relationship failed to reach significance for patients after a Holm–Bonferroni correction. The difference between these correlations in the two groups was statistically significant. In both groups, objective memory performance and self-assessment of memory (assessed by MMQ ability, MMQ Satisfaction, and STIDA) were not significantly correlated. Conscientiousness and the interactions of group with conscientiousness and executive function were the strongest predictors of memory self-assessment as measured by MMQ ability. Our results suggest that memory self-assessment is not accurate, and is better predicted by conscientiousness and executive functions than by memory itself. Clinicians should know about the potential lack of accuracy of memory self-assessment when screening for memory impairment. Memory concerns reported by patients may not translate in objective memory impairment. At the opposite, confidence in memory may not reflect normal memory functioning.