Sea-ice algae contribute substantially to primary production in ice-covered oceans, and ice-associated organic matter plays an important role in polar marine food webs. A better understanding of the sympagic (ice-associated) food webs is necessary for quantification of the sympagic food sources available to planktonic and benthic organisms and for estimation of the impacts of climate change on polar marine ecosystems. Sympagic meiofauna – proto- and metazoans >20 µm inhabiting the brine channels of sea ice – have generally been assumed to feed on sea-ice algae and their grazing pressure has been estimated to be usually low. Our study, in contrast, shows that sympagic meiofauna is an important component of the Arctic and Antarctic sympagic food webs. We applied a three-fold approach to study the trophic role of sympagic metazoan meiofauna. Abundance analyses allowed an assessment of the community structures and an estimation of the contributions to sea-ice particulate organic matter. Analyses of stable isotopes of carbon and nitrogen on one hand, and of lipids and fatty acids on the other, revealed trophic positions, diets and feeding strategies in situ. Feeding experiments gave additional information on diets, feeding selectivity and ingestion rates of various taxa. Viewed in conjunction, these different approaches revealed an overall picture of the sympagic food web and, with the aid of mathematical modelling, enabled us to give more realistic estimates of the feeding impact of sympagic meiofauna. We could show that these animals exhibit diverse feeding strategies, causing the sympagic food web to be more complex than generally assumed. Furthermore, ingestion rates and biomass can be high, and can result in considerable feeding pressure. We discuss the influence of meiofauna feeding activity on the dynamics of sympagic communities and on food availability to under-ice fauna and pelagic animals. We conclude that meiofauna cannot be neglected in studies on polar marine food webs.