According to the United Nations more than half of humanity live today in cities, and by 2050 seventy percent of the world’s population is projected to be urban. This means that there will be a transformative role of cities at all levels in the coming decades. In general, Local governments have the responsibility to provide their people with basic services to improve their living standards because democracy is also measured in terms of quality of life and the common good. Through the case study of Los Cabos Citizen Observatory (ICO) in Los Cabos, Baja California Sur, Mexico, we have analyzed and learned that a conscious, competent, credible, collective, collaborative, continuous and communicative citizen par-ticipation can occur with the use of ISO 18091 international standard. With this tool, not only can citizens evaluate the administration's action in an integral way but also offer pro-posals of value for the improvement of public services and policies which eventually be-come strategic axes of municipal development plan for a good governance. Therefore, ICOs are Building a Reliable Citizen Participation for Local Government which can be pre-sented as 'one valid global way' to improve Democracy and Participation in the 21st cen-tury that are promoted and practiced starting from the cities.