The rapid urbanization of the developing world is giving rise to a host of concerns about the implications of “fragile” cities in relation to security, development and humanitarian action. Presently, more than half of the world resides in cities, and the latest projections reveal that this will rise to almost three quarters by 2050 or 7 billion people. The majority of global urban population growth will be concentrated in large and intermediate cities and their sprawling informal settlements in low-income settings. The refocusing of policy makers on the city is also taking place against an apparent decline in inter- and intra-state conflict over the past two decades and an apparent surge in more acute forms of organized violence associated with networked armed groups and criminal gangs. A debate is brewing on the scope and scale of urban violence in the twenty first century, the challenge this presents to the humanitarian sector, whether and in what ways the humanitarian community should respond. This article offers some preliminary observations on trends in urbanization and urban violence with insights from the security studies and urban geography literatures. Drawing on the experiences of practitioners, it also introduces some reflections on how humanitarian actors are coming to terms with chronic and acute forms of urban violence. It makes the case for humanitarian agencies to more robustly and comprehensively engage with the causes and consequences of urban violence and argues that practitioners must expand the lens of analysis to consider the specific humanitarian needs of populations affected by endemic urban violence.