A growing majority of the world's population lives in cities. This rapid urbanization increases the concentration of people and critical services in cities, which also upscale their exposure to acute shocks and long-term stresses such as floods, earthquakes, climate change or social dynamics. While all of these challenges are complex in themselves, in most cases, cities must face a combination of them. Resilience thinking demands cities plan holistically so that they are prepared for whatever shocks and stresses may arise. Although there is a set of frameworks aimed at building city resilience, frameworks specifically aimed at operationalizing the resilience-building process within cities remain undeveloped. This research begins to fill this gap by developing a Resilience Maturity Model (RMM) that provides cities with a roadmap for operationalizing the resilience-building process. For that purpose, the RMM defines a sequence of maturity stages and a set of policies that help cities to assess their current maturity stage and identify the policies that need to be implemented to improve their resilience level.