Current socio-economic and infrastructures development efforts are sustained by the use of environmental resources. This, sometimes, may leave environmental deleterious effects if the principles of sustainable development are not well integrated into development planning. It is against this background that sustainable cities, green building or sustainable construction as well as green economy are all embraced by sustainable development principles as the drivers of human welfare which support the theory of environmental sustainability and sustainable utilization of natural resources. The purpose of this article was to analyse urbanization trends and green development policies globally, with a particular focus on Rwanda, looking at green cities and green buildings. The findings from the study revealed that the world’s areas are urbanizing with an increase in more urban residents in different countries because the United Nations’ projections show that percent of urban will move from 29.6% in the year 1950 to 66.4% in the year 2050. The same trend in urban residents was projected in Rwanda where the Government of Rwanda identified an urbanization target rate of 35% by 2020 whereas UNPD projected 33.5% urban growth for Rwanda by 2020.The projections show that with the current ongoing development, this trend will continue in six secondary cities of Rwanda. Rubavu and Musanze cities followed by Nyagatare city are expected to have an increasing number of urban population. But, urban households are projected to increase in Rubavu city (36.7%); Nyagatare city (20%) and Musanze city (17.7%) in the year 2020. As the result, Rwanda has developed Green Growth and Climate Resilience “National Strategy for Climate Change and Low Carbon Development”, the National Roadmap for Green Secondary City Development, introduction of Rwanda Building Code and the National Housing Policy together with the creation of Rwanda Green Building Organization (RWAGBO), the Rwanda Green Building Minimum Compliance System, etc. led this green transformation for cities in Rwanda. Now Rwanda is one of the leading countries for green growth in Africa and a member country of Global Green Growth Institute (GGGI). Enhancing the role of policy and green development strategies with sound liabilities rules will drive the green growth vision in order to sustain green economy with sustainable cities.