Urban parks are important elements of city green infrastructure. Many studies highlight their positive influence on the quality of life and human well-being as well as their significance for sustaining natural processes in built-up areas. For the last decade, much has been written about urban ecosystem services (ES), however in comparison with the abundance of studies on the potential for delivering ecosystem services by different land use and land cover types, research on the capacity of parks to deliver these services depending on site-specific elements, is relatively uncommon. Thus, this paper reports on research that explored levels of local regulating and cultural ecosystem services delivered by Warsaw parks, as these services are considered as the most important for urban dwellers. The authors based the study on data included in existing policy documents related to environmental and spatial planning for Warsaw, and evaluation of Warsaw green spaces. The assessment included 10 ecosystem services: micro-climate regulation, air quality regulation, noise reduction, balancing rainwater peaks, recreation, social inclusion, physical health benefits, nature experiences, aesthetic appreciation, and sense of identity. The assessment was performed for all Warsaw public parks, covering an area over 2 ha (n = 82). The results enabled us: (1) to assess all parks with respect to their actual impact in delivering 10 studied ecosystem services; (2) to designate their potential capacity to deliver regulating and cultural services; and (3) to allocate all assessed parks into categories that represent their predominant character (multifunctional, with cultural advantage, with regulating advantage or without any predominant function).