Aktopraklk is a settlement site composed of three areas (A-C) in the Marmara region of northwest Anatolia, with phases of occupation that date to the Late Neolithic and Early Chalcolithic periods, mid-seventh to mid-sixth millennium bc (ca. 6400-5600 cal. bc). Here, we present 54 human and fauna bone collagen stable isotope results from the site, alongside five modern fish bone collagen isotope results, to examine the nature of human diet. The stable isotope analysis shows that human diet comprised the consumption of select C-3 terrestrial resources, with a preference for domestic animal proteins over plant proteins. The evidence to date suggests that animal husbandry was at the forefront of Late Neolithic and Early Chalcolithic subsistence practices. No isotopic difference in humans is observed between biological sex or between areas B and C at the settlement.