The paper is an attempt to verify the hypothesis about the positive effects of infrastructure investments on sustainable development of Siedlce city. For this purpose an analysis of selected investment by the city of Siedlce in 2010-2015. Also conducted a study (free interview) with a spokesman for the Office of the City of Siedlce, the aim of which was to verify the individual investments to satisfy the conditions for sustainable development results showed that the biggest investment by the city of Siedlce actually fit in with the idea of sustainable development.