Extant sociological research on why some communities are more prone to crime than others rely on theories of social disorganization, which argues that neighborhood ethnic heterogeneity fractures community solidarity, which in turn, increases crime. However, such research has failed to examine how the effects of neighborhood ethnic heterogeneity vary by city level racial segregation. Drawing upon Peter Blau's theory of social structure, in this thesis, I propose that city racial segregation creates a social environment that constrains intergroup relations and engenders feelings of alienation toward the dominant society. I find that under such conditions, the social cohesion consequences of neighborhood ethnic heterogeneity operate differently. When cities are integrated, ethnic heterogeneity disrupts community solidarity, which, in turn, increases crime. However, under conditions of widespread city racial segregation, where race becomes highly salient, the effects of ethnic heterogeneity on crime weaken because it serves to reduce the harmful effects of social isolation.