Laboratory-reared stage C5 copepodites of the marine calanoid copepod Calanus finmarchicus were used to test the effects of temperature (at 6°C, 12°C and increasing temperature stress from 6-12°C) and prey type (the dinoflagellate Heterocapsa triquetra, abbreviated "Het", and the diatom Thalassiosira weissflogii, abbreviated "Tw") on the extent and efficiency of dietary EPA and DHA incorporation from phytoplankton to copepods in a set of feeding experiments using 13C labelling. These data depict ingestion, incorporation and gross growth efficiency (GGE), defined as the fraction of ingested EFAs retained in copepod tissue, of both EFAs in different temperature treatments in 8-day laboratory feeding experiments.