Numerous wild species have managed to adapt to the specific conditions of the urbanized environment. Wild animals take advantage of the microclimate conditions and the available hiding places or food; however, they are also exposed to various risks in this environment. The aim of this study was to determine the causes of incidents between wild mammals and human infrastructure and activity in the city of Warsaw and to evaluate the effectiveness of an animal rehabilitation center. The second aim was to assess the factors (weather and land cover) that influence incidents involving wild mammals in Warsaw. We found that human infrastructure and activity cause most of the wild mammal incidents in the city. The frequency of small mammal incidents in Warsaw was dependent on the weather, mainly the ambient temperature. The proportion of built-up areas was usually associated with the number of such incidents. This relation was positive for species that tend to live in cities, and it was negative for species that avoid human proximity.