Intercontinental exchanges between communities living in different parts of Eurasia during the late prehistoric period have become increasingly popular as a topic of archaeological research. The Qijia culture, found in northwest China, is one of the key archaeological cultures that can shed light on trans-Eurasian exchange because a variety of imports are found in this cultural context. These imports include new cereals and animals, which suggest that human diets may also have changed compared with previous periods. To understand human and animal diets of the Qijia culture, carbon and nitrogen isotope ratios from human and animal skeletal remains were analysed from the type site of the Qijia culture at Qijiaping. The results demonstrate that human diet at the site mainly consisted of millet and animals fed on millet. C3 cereals, such as wheat and barley, did not contribute significantly to human diet, and no isotopic differences were found between adult and subadult diets. Furthermore, three outlying human results raise the possibility of exogenous individuals, perhaps in relation to the parallel movement of animals, crops and goods. This study provides human and animal dietary information for evaluating the nature of exchange and diffusion in eastern Eurasia at this time. Copyright © 2013 John Wiley & Sons, Ltd.