In this article we present an isotopic analysis of human bone collagen (δ13Ccol, and δ15Ncol) and bone apatite (δ13C) for diet reconstruction, as well as δ18Oap of human bone apatite for climate reconstruction, using samples from Northern Greece. Radiocarbon dating analysis was conducted on three of the Agras samples and the results (from 1000 to 800 BC) correspond to the Early Iron Age. Isotopic values for δ13Ccol range from −20.5‰ to −16‰ and for δ15Ncol from 6‰ to 11.1‰—a strong indication of a C3-based diet, with contributions by C4 and freshwater fish elements. The results were compared to the ones from Roman Edessa, and Alexandreia (a contemporary city near Edessa), as well as to other Early Iron sites in Greece and wider Europe. In general, the results from Agras are in good agreement with the results from Northern Greece, with the exception of the Makriyalos site, and are quite close to those of Croatia’s and Hungary’s sites. Additionally, from the δ18Oap results we calculated the oxygen isotopic composition of consumed water for Agras (from −9.6‰ to −10.9‰) and for Roman Edessa (from −9.6‰ to −11.2‰) for the palaeoclimate and palaeomobility reconstruction.