With obesity-related health problems on the rise among older Americans in the past few decades, physical activity has been a major focus in the fight to overcome the obesity epidemic. The evidence to date suggests that the built environment, specifically walkable neighborhoods and features, is associated with physical activity among all ages. This study examined the associations between environmental walkability and physical activity levels of older adults, and compared the data in two different areas of two cities: the downtown and suburban-rural sites of San Diego, CA and Ithaca, NY. Results indicate similar physical activity levels among older adults in objectively walkable, downtown sites versus less walkable, suburban/rural sites, and suggest perceived neighborhood environment and personal factors as particularly significant factors. Specifically, neighborhoods that were perceived to have high diversity of land use mix, aesthetic attributes, and walking and cycling facilities were significantly associated with higher physical activity. Recommendations are also given regarding the importance of examining other factors such as weather, acculturation, walking purpose, and travel mode, to further understand the complexity of the relationship between the physical environment and older adults' physical activity.