Assessment of the impact of climate change on the Arctic nearshore ecosystems requires knowledge of the “reference points”, that is, the state of things before the effects of the warming become pronounced. For parasites, which play an essential role in the nearshore ecosystems, this knowledge is scarce and fragmentary. This study, based on the materials collected at Franz Josef Land (FJL) in 1990–1993, partly fills this gap. We present the first data on the diet of the common eider Somateria mollissima at FJL, the transmission of helminths in its population and the infection of nearshore invertebrates with helminth larvae. We found that gastrointestinal helminth communities were impoverished (only ten species) and dominated by cestodes and acanthocephalans. This is associated with the prevalence of nearshore crustaceans, the intermediate hosts of these helminths, in the diet of the eiders. The absence of the vulnerable free-living larvae also facilitates transmission of helminths parasitizing eiders at FJL. Infection with helminths and the diet were different in ducklings and in adult birds as well as in eiders from different parts of the archipelago. The infection distribution of molluscs and crustaceans with helminth larvae was patchy and higher in the vicinity of the eider colonies. A high-infection intensity of FJL eiders with cestodes and acanthocephalans recorded in our study seems to have a certain negative effect on the bird population. Its significance is likely to grow considering that the transmission of helminths is promoted by the climate warming in the Arctic.