The Hakon Mosby mud volcano (HMMV) is one of the most studied cold-seep sites in Europe. Its exceptional fluid expulsion activity and large geochemical gradients from the centre to the periphery support dense biological communities and induce spatial heterogeneity in microbial activity and faunal zonation. At this site, the macrofauna has been little studied and the variability in its macrobenthic nutrition has not yet been investigated. In this study, based on the analysis of the stable isotopes of carbon and nitrogen, we determined nutritional patterns for macrofauna communities in three different habitats (microbial mats, sediment adjacent to the mat and Siboglinidae polychaete fields). delta C-13 values of macrofaunal tissues varied among two habitats (microbial mats and Siboglinid fields), with lighter mean signatures on microbial mats (-46.9 parts per thousand) than in Siboglinidae fields (-27.0 parts per thousand). However, no small-scale variability was revealed between mats and adjacent sediment. The dominant carbon source in macrofaunal nutrition was chemosynthetically fixed and the bulk of organic carbon was derived from sulphur-oxidizing bacteria. However, the variability of delta C-13 and delta N-15 signatures of macrofauna within this habitat suggests the co-occurrence of two food chains on mats, one based on sulphur-oxidation and the other based on aerobic or anaerobic methanotrophy.