Neighborhood physical disorder-the visual indications of neighborhood deterioration-may inhibit outdoor physical activity, particularly among older adults. However, few previous studies of the association between neighborhood disorder and physical activity have focused on this sensitive population group, and most have been cross-sectional. We examined the relationship between neighborhood physical disorder and physical activity, measured using the Physical Activity Scale for the Elderly (PASE), in a three-wave longitudinal study of 3497 New York City residents aged 65-75 at baseline weighted to be representative of the older adult population of New York City. We used longitudinal mixed linear regression controlling for a number of individual and neighborhood factors to estimate the association of disorder with PASE score at baseline and change in PASE score over 2 years. There were too few subjects to assess the effect of changes in disorder on activity levels. In multivariable mixed regression models accounting for individual and neighborhood factors; for missing data and for loss to followup, each standard deviation increase in neighborhood disorder was associated with an estimated 2.0 units (95% CI 0.3, 3.6) lower PASE score at baseline, or the equivalent of about 6 min of walking per day. However, physical disorder was not related to changes in PASE score over 2 years of follow-up. In this ethnically and socioeconomically diverse population of urban older adults, residents of more disordered neighborhoods were on average less active at baseline. Physical disorder was not associated with changes in overall physical activity over time.