During the 2014 BICOSE cruise of RV Pourquoi Pas ? (Cambon-Bonavita 2014, https://doi.org/10.17600/14000100), biomass-dominant fauna was sampled in two deep-sea hydrothermal vent fields: Snake Pit and TAG (Mid-Atlantic Ridge). Stable isotope ratios and elemental contents of carbon and nitrogen of 137 samples belonging to 21 taxa were measured. Samples were identified and frozen at -80°C on board, then brought back to the laboratory for processing. They were prepared for analysis at the LEP (Laboratoire Environnement Profond, Ifremer, Centre de Bretagne, France; https://wwz.ifremer.fr/deep_eng/). Analytical measurements were performed at the LIENSs stable isotope facility (University of La Rochelle, France; https://lienss.univ-larochelle.fr/isotopic-spectrometry). The dataset consists of two files: one containing the data itself, and one describing all used terms (measurements or metadata).