We examined whether the prevalence of commercial diversity, heavy traffic, sidewalks, and trees is associated with perceived social cohesion in Los Angeles County neighborhoods, and how concentrated disadvantage and perceived danger shape these relationships. Consistent with theoretical expectations, concentrated disadvantage and danger were associated with lower cohesion. The effects of built characteristics on cohesion were moderated by disadvantage and/or perceived danger. Danger moderated the effect of commercial diversity, sidewalks, and trees, and concentrated disadvantage moderated the coefficients on built variables (excepting trees) such that the magnitude of their effects were stronger in high-disadvantage neighborhoods. We conclude that built characteristics appear to matter more for cohesion in high-disadvantage neighborhoods and also that approaches to promoting cohesion through the built environment should focus on bolstering residents’ perceptions of safety.