The aim of the study was to compare helminth community structure of urban and forest blackbird populations. 24 helminth species in 98 blackbirds were found. Higher species richness was noted in the forest population of the blackbird (23 species) in comparison to the urban population (14 species). The response of the helminth fauna to a synanthropic habitat, contrary to a natural habitat, consists in a significant reduction in most parasitological parameters. Higher species richness has been noted in spring (17 species) than in autumn (14 species). Urban habitat, in contrast to the forest, may cause changes in the abundance of helminth communities in male and female blackbirds. The helminth fauna of nestlings, in spite of low species richness is characterized by a higher prevalence and intensity of infection in comparison to blackbirds feeding on their own. Helminth fauna of the blackbird seems to be a good indicator of environmental quality.