The purpose of this dissertation was to explore, through a social ecological framework, the multifaceted effects of the neighborhood environment by investigating how dimensions of both the built environment and the neighborhood social context may interact to influence walking. Aesthetics, land use mix, crime, and pedestrian infrastructure were considered with respect to built environment walkability, and the neighborhood social context was conceptualized using measures of both social cohesion and social interaction with neighbors. This research used data from an Environmental Protection Agency (EPA)-funded study of 748 adults (18 years of age and older) residing in the Lents neighborhood in Portland, Oregon. Through a series of both multiple linear and logistic regression models, the analyses examined the specific pathways by which social interaction with neighbors, social cohesion, and age influenced the relationship between the built environment and walking behavior. Results suggest that both social interaction and social cohesion but not age moderate the effects of the built environment on walking. There was evidence of mediation, as well, for both social interaction and social cohesion. The implications of these findings for future research and policy are discussed