The consequences of climate change are increasingly present in our lives, and it is inevitable that we will have to adapt. This adaptation must be swift and proactive. That is why the European Union has decided to accelerate the adaptation process and, in accordance with the Paris Agreement, has adopted the European Green Deal, which is a guideline for meeting the main goal of the European Union - become a climate-neutral continent by 2050. This is where cities and urban areas come into focus, which, although they occupy only 4 % of the area of the European Union, are home to 75 % of the population. Cities produce more than 65 % of the world's energy and account for more than 70 % of the world's greenhouse gas emissions. In accordance with the above, this thesis will look at the role of cities in reducing greenhouse gas emissions and negative impact on the environment. It will provide an overview of the areas that city authorities have influence on and can manage to encourage sustainable urban development. Existing methodologies for the development of green city development strategies as a key approach for creating a sustainable urban environment will also be analyzed. Guidelines in various sectors set by the European Union and the European Bank for Reconstruction and Development will be explored. The thesis will focus on the strategies that have been applied in different cities around the world, the research will analyze the effectiveness of these strategies, identify their advantages and disadvantages, and consider the challenges in implementation.