Since the second half of the 20th century, sustainable development has been one of the main challenges for the contemporary world. The realization that natural resources can be exhausted has led to changes in the approach to development priorities in many societies. The global nature of these challenges has generated methodical attempts to find solutions to these challenges and identify necessary actions (UN conferences). The progressing urbanization, expressed both in the number of cities and the population living in them, has exacerbated negative effects by concentrating many people in a limited space. This issue has attracted attention of the international community. However, apart from solutions proposed at the global level, actions at the local level are considered necessary. Although so far the scale of such actions has not been imposing (every action fits the size of a city), they are already capable of producing satisfactory results. While harmonizing urban development, a participatory budget can be used to allow citizens to decide on the nature and type of investments in the city. Selected projects often follow sustainable development principles, as citizens want to improve the quality of life by making their environment more livable. The aim of the study is to analyze projects submitted and selected by citizens under the participatory budget and to assess their impact on urban sustainability based on the example of Szczecin, Poland.