The article explores the reasons why urban public policies in Latin America have a very high degree of complexity. It also addresses the challenges that this generates for local governments. It examines in an illustrative way the case of Medellin (Colombia) by taking as a point of reference urban regeneration policies applied during 2004-2015. The complexity of urban policies can be exposed in aspects such as follows: In urban policies it is necessary to give room for diverse and sometimes conflicting interests; Latin American cities are faced with the challenge of ensuring, simultaneously with its policies, not only the human development but also the competitiveness required by the globalized world of today. Finally, it is increasingly clear that policy makers must take into account the consequences of the urban transformation processes that result from public policies. This work continues by evidencing the main tensions that complexity imposes on public policies concerning urban transformation in Latin America.