Parasites are recognised as an excellent source of information on the distribution of their hosts. Here, the macroparasite fauna of 20 species of Pleuronectiformes belonging to five different families and inhabiting the Portuguese coast was investigated and compared with that known in four other areas (the North Sea, north Northeast Atlantic, Mediterranean Sea and Northwest African coast) in order to determine (1) their zoogeographical pattern and (2) the role of the Portuguese coast as an intermediate biogeographic province. Macroparasites infecting Pleuronectiformes sampled along the Portuguese coast were collected using standard parasitological techniques, whereas data on those in the other four areas were obtained from the literature, rendering a total of 73 macroparasite species. Both sets of data were then compiled in a presence/absence matrix. Hosts and macroparasites were placed into zoogeographical categories according to their known distribution, and patterns were evaluated using multidimensional scaling and cluster analysis. The zoogeography of hosts and parasites was not entirely concordant, although that of endoparasites was generally consistent with the patterns for marine free-living species. On the other hand, only specific ectoparasites truly mirrored the distribution of their hosts. These differences reflect the importance of host ecology and dispersal and environmental factors on the patterns revealed. The Portuguese coast seems to play a significant role in the distribution of Pleuronectiformes’ parasites along the Northeast Atlantic and Mediterranean Sea, due to its transitional character and to the sympatric occurrence of related hosts, both promoting the acquisition of new parasite species or the maintenance of historical host-parasite relationships.