Households age 60 and older bear increasing responsibility for managing retirement portfolios, and they hold the majority of financial assets in the United States. Cognitive aging studies find evidence of a decline in fluid and crystallized intelligence in old age that may impact the ability to manage money effectively. Using a large sample of older respondents, we test whether knowledge of basic concepts essential to effective financial choice declines after age 60. We find a consistent linear decline in financial literacy score after age 60. A nearly identical rate of decline among men, stockowners, older, and college-educated respondents indicates that cohort effects are not driving the results. Confidence in financial decision-making abilities does not decline with age. A separate analysis using data that include measures of cognitive ability suggests that a natural decline in both fluid and crystallized intelligence in old age contributes to falling financial literacy scores. This paper was accepted by Brad Barber, finance.