The World Health Organization promotes Age-Friendly Cities to achieve more appropriate environments for older people. This paper reviews the updated literature linked to AFC and some existing models for assessment of age-friendliness. The desk review concludes that models should be further developed in vulnerable areas; moreover, models should be easily adaptable to different urban contexts, by using practical tools to evaluate the actual problems faced by older people. A model for assessing vulnerability of neighbourhoods from this view has been applied in a neighbourhood in the region of Guanajuato (Mexico). The results have been compared with the results in a vulnerable neighbourhood in Castelló de la Plana (Spain), using the analogical method. An expert-driven selection of indicators is carried out by a group of multidisciplinary professionals with deep knowledge of the area, measuring and adapting the indicators to the site, by implementing the inter-judges agreement technique. This contribution, together with the existence of sufficiently disaggregated information, allows for the calculation of a global index made up of indices by dimensions that provide information on priority interventions in the area and the application of sectoral policies. The comparison with a previous case study in Spain allows us to infer some aspects to learn from good practices and bring out the full potential of the model. The model has proven to be practical and applicable transnationally. The comparison with a case study where the problem of ageing is a long-standing concern may be useful for the authorities.