How does rapid urban growth affect risks of communal violence in cities? In rapidly growing cities, poor planning and weak institutions combined with an unregulated influx of migrants can create a potent recipe for violent mobilization. In addition, politicized identity groups often compete for resources and interact in close proximity in urban areas. Despite a growing research agenda on the relationship between rapid urban growth and urban violent unrest, findings remain inconclusive. One explanation for the disparate conclusions is that the theoretical pathways connecting urban growth and unrest largely fail to consider both the violence-generating and violence-stemming effects of urban growth. With a focus on conflict-ridden societies, we theorize processes through which urban growth influences different aspects of group relations in the city, and thereby contribute to prevent, suppress or generate communal violence. To illustrate the framework, we draw on insights from Nairobi, Kampala and Addis Ababa. By paying attention to processes, we are able to identify a range of developments associated with city growth which in turn have different implications for communal violence.