In this study, the subsistence patterns of two prehistoric communities on the island of Euboea were reconstructed using carbon and nitrogen isotopic compositions of human and faunal bone collagen. The Late Neolithic (5300/5200–3300/3200 BC) samples were obtained from Tharrounia (human n= 14, faunal n= 4), while the Early Bronze Age (2900/2850-2350/2300 BC) skeletal specimens derived from the coastal settlement of Manika (human n= 107, faunal n= 7). The average δ¹³C value of human isotopic signatures of Tharrounians was consistent with a C3 terrestrialbased diet. Mean δ15N value indicated a diet mainly focused on agricultural products with a systematic exploitation of animal protein (ie meat and/or milk products), whereas marine resources were not an important component of Late Neolithic diets. With regard to the inhabitants of Manika, δ¹³C values indicated that all individuals also had a C3 terrestrial-based diet. In terms of nitrogen isotope values, these suggested that the majority of the individuals were consuming animal products on a regular basis and in comparatively higher amounts than the Late Neolithic population at Tharrounia. Besides the contributions from animal and plant protein, the distribution of δ15N values showed that some individuals could have supplemented their diets with small amounts of marine food or their δ15N values could have been increased as a result of manuring of the crops. Finally, isotopic data pointed out that overall there was a relatively low level of social differentiation as there was little variation in the diet between different groups of individuals in both prehistoric settlements.