We present data of Atlantic bluefin tuna (Thunnus thynnus) diet published in Ólafsdóttir et al (2016). Each line corresponds to the observation of one prey individual in a single tuna stomach and contains data on the predator (tuna ID number in database, length, weight and sex) and on the prey (Micromesistius poutassou, Gonatus fabricii, Todarodes sagittatus, Scopelogadus beanii, Notoscopelus kroeyeri, Maurolicus muelleri and Paralepidae), together with cruise information (latitude, longitude and date of collection). Therefore, several lines can contain data of a single tuna stomach which can be identified by the “Specimen ID (predator, MFRI database)” column. The size, weight and length of each prey was recalculated based on regression between beak/otolith size and total length of the prey estimated from survey samples collected in Icelandic waters. These regressions are available under "Further details".