Objectives: We examined the association between walkability of the built environment and changes in physical performance among women aged 65 or older (n = 1,671, 253 neighborhoods). Method: Street connectivity and street density, markers for neighborhood walkability, were assessed through linkage to secondary data sources. Physical performance was measured with timed-walk and chair-stand tests assessed during follow-up visits about every 2 years for 12 to 14 years. Multilevel models predicted change in physical performance, controlling for age, number of incident comorbidities, self-rated health, and death during follow-up. Results: Overall, physical performance declined during follow-up (p < .001). Neighborhood walkability had no effect on change in physical performance among women who reported not walking at baseline. However, among women who walked, greater neighborhood walkability was associated with a slower decline in dynamic leg strength, indicated by score on chair stand. Discussion: Neighborhood walkability may protect against decline in physical performance.