This chapter examines a comprehensive urban policy approach to urban security adopted in the early 2000s in Medellin to reduce violence and marginalization. Such approach recognized violence, socio-spatial exclusion, and institutional fragility as endemic and interconnected problems. Recognizing that chronic violence cannot simply be overturned with orthodox policy tools, Medellin’s policymakers experimented with a coordinated strategy involving area-based planning, social investments, civic engagement, violence prevention programs, and strategic policing. Between 1991 and 2015 violence rates dropped by almost 90 percent. The chapter explains the factors that contributed to the rise and decline of chronic violence, and the role of innovative urban policy in promoting human security and social sustainability. It concludes by noting that current security policies have departed significantly from previous programs that aimed to support a citizen-centerd, human security model, including community participation and social development. Social investments have been increasingly supplanted by larger budgets for policing and security technologies. Building equity remains a key challenge to Medellin’s current social sustainability; a city where a large proportion of the population is still socio-economically excluded and where the rule of law continues to be applied selectively.