When ethnic conflict is likely people seek safety in homogenous neighborhoods, but does the resulting ethnic segregation decrease communal violence? This paper argues that local segregation causes violence by eroding interethnic trust. Although segregation reduces violent disputes between individuals, the possibility of positive interethnic contact is also lower in segregated areas. Where levels of interethnic trust are low, it is easier for political leaders and other extremists to build support for communal violence. I demonstrate that segregation increases the incidence of violence using a new data set measuring ethnic composition and violence across approximately 700 small localities in Kenya's Rift Valley Province during Kenya's 2007/2008 post-election crisis. Because segregation is likely endogenous to violence, I draw on Kenya's history of land settlement to instrument for segregation. I also demonstrate that it is unlikely local segregation increases violence by increasing groups' organizational capacity for violence.