Barcın Höyük is one of the oldest Neolithic settlement sites in northwest Anatolia, with early layers of occupation radiocarbon dated to ca.6600 cal BC. The Neolithic phase at the site (ca.6600 – 6200 cal BC) has seven layers of occupation, and shows a number of affinities, in terms of structure and zooarchaeological remains, with contemporary sites in the coastal area near Istanbul (Özdoğan, 2013). The available zooarchaeological evidence suggests a diet of terrestrial fauna, with some inclusion from freshwater aquatic species. This study investigates the nature of human diet at Barcın Höyük through carbon and nitrogen analysis of human and animal bone collagen, and examines whether there is any isotopic evidence for a shift in diet after the re-organisation of the site at ca.6200 cal BC. Here we present 75 human and faunal analyses from the Neolithic layers at Barcın Höyük. Two new radiocarbon dates on human skeletons are also included in the study.