AbstractThe Ji'erzankale Necropolis (吉尔赞喀勒墓地) is located on the Pamir Plateau in the Xinjiang Uyghur Autonomous Region of China. Composed of numerous stone circle graves and directly radiocarbon dated to the Iron Age (ca. 2400–2600 years cal BP), this site is unique in that numerous lines of archaeological evidence suggest that those interred here were followers of the Zoroastrian religion. Here, we present carbon (δ13C) and nitrogen (δ15N) stable isotope ratio measurements of seeds (Nitraria pamirica, n = 7), animals (n = 14), and humans (n = 24) to reconstruct ancient diet and lifeways at the Ji'erzankale Necropolis. The results of the N. pamirica reflect the natural C3 vegetation and arid environment of this region. The δ13C (mean ± SD = –18.6 ± 0.8‰) and δ15N (mean ± SD = +8.1 ± 1.6‰) results of the animals (13 sheep and 1 hare) display a mostly C3 terrestrial diet with variable levels of protein consumption. Adult humans (n = 19) have δ13C (mean ± SD = –17.9 ± 0.2‰) and δ15N (mean ± SD = +13.1 ± 0.3‰) results that tightly cluster above the sheep by approximately +5‰. This is evidence that the diet of this population was relatively homogenous and mainly based on sheep and/or their secondary products and did not have a large input of C4 crops such as foxtail (Setaria italica) or common millet (Panicum miliaceum).