Recent studies in public health have focused on determining the influences of the built environment on the population’s physical and mental health status. In order to promote active transport and physical activity, considered favorable behavior for the prevention non-communicable diseases (NCDs) such as obesity, it is necessary to reduce the negative effects of the built environment and develop positive ones, such as, for example, a walkable urban space. The aim of the research is to define a city’s walkability assessment framework capable of highlighting points of strength and weakness in its urban environment. All of the aspects that have a direct influence (evidence-based) on fostering the adoption of healthy lifestyles or promoting active transport as a strategy to increase the level of physical activity due to the existence of daily urban travel should be considered. After conducting a literature review aimed at identifying all of the existing assessment tools, 20 research studies were examined in detail. The new evaluation method arises from the comparison and critical selection of the various qualitative–quantitative indicators found, integrated into a multi-criteria analysis structure of dual-scale survey, with reference to walkability and paying attention to those indicators that have implications on health promotion. The new assessment framework, named Milano Walkability Measurement (MWM), is applicable in different urban contexts and was tested in two different areas of Milan. The Macro dimension (i.e., Density, Diversity, and Design criteria) refers to the urban scale and examines the city from a top view. It describes quantitatively the overall urban factors (urban area size equal to 1.5 Km2; typology of data: archival). The Micro dimension (i.e., Usefulness, Safeness, Comfort, and Aesthetics criteria) investigates the city at the street scale level. It describes qualitatively features of the outdoor spaces (road length of about 500/700 mt; typology of data: observational). Finally, the framework was weighted by comparison with a panel of experts. The expected results were reflected in the design recommendations based on the collected qualitative-quantitative data. The developed assessment method brings innovative criteria such as the multi-scaling assessment phase (Macro and Micro) and the ability to take into consideration aspects that according to the literature have relationships with health promotion linked to the improvement of a healthy lifestyle, related to daily active transportation choices. The design recommendations are useful both to policy-makers, to make evidence-based specific choices, and to designers, to understand what aspects of the urban environment must be improved or implemented in order to promote a walkable city.