Diet data for Atlantic cod (Gadus morhua), saithe (Pollachius virens), capelin (Mallotus villosus), Atlantic herring (Clupea harengus) witch (Glyptocephalus cynoglossus), long rough dab (Hippoglossoides platessoides) and whiting (Merlangius merlangus) from Ullsfjord in Troms County, Norway, during 2010. Cod were sampled from shallow water (file: Diet_G_morhua_Ullsfjord_2010_shallow, average depth of 15 m) using fish rod and from deep water (file: Diet_G_morhua_Ullsfjord_2010_deep, average depth of 280 m) using a shrimp trawl. Saithe (file: Diet_P_virens_Ullsfjord_2010.txt), whiting (file: Diet_M_merlangus_Ullsfjord_2010.txt), witch (file: Diet_G_cynoglossus_Ullsfjord_2010.txt), long rough dab (file: Diet_H_hippoglossides_Ullsfjord_2010.txt), capelin (file: Diet_M_villosus_Ullsfjord_2010.txt), herring (file: Diet_C_harengus_Ullsfjord_2010.txt were also sampled at deep water using shrimp trawl. The data was collected and analysed as part of the project: Investigating coastal ecosystem structure and dynamics using Ecopath/Ecosim ecosystem models and stable isotope data. Proportions wet weight of various prey groups were estimated based on stomach analysis. The data is used in the publication: Pedersen, T., Ramsvatn, S., Nilssen, E.M., Nilsen, M., Morissette, L., Ivarjord, T., Systad, G.H., Kolsum, I., Fause, H., 2016. Species diversity affects ecosystem structure and mass flows in fjords. Regional Studies in Marine Science 3: 205-215. doi: 10.1016/j.rsma.2015.10.007