Cryptosporidium spp. and Giardia spp. are intestinal protozoan parasites that are prevalent and widespread pathogens of humans and many other species of mammals. The aim of this review is to summarise the last 20 years of research on the epidemiology of these parasites, with a particular emphasis on the environment and the role played by different groups of animals in Poland. The prevalence of both species has been studied in different groups of humans, in wildlife, pets and farm animals and in environmental samples. Additionally, current knowledge on the distribution of zoonotic and non-zoonotic species/genotypes has been reviewed. The usefulness of different methods for the detection and identification of the parasites in different types of samples has been evaluated. Finally, because of the wide distribution and high prevalence of both species in a range of hosts and possible vectors involved in mechanical transmission, the overall risk of outbreaks of cryptosporidiosis and giardiosis in Poland has been assessed as relatively high.