This study reports the results of stable isotope analyses (carbon, nitrogen and sulphur) of human bone collagen from the Sunhung mural tomb from the Three Kingdoms Period of Korea (AD 300–668). The stable isotope data indicate that the main source of protein in the diet of the interred seven Sunhung individuals came from C3‐based terrestrial resources, and there was an isotopic variation between individuals at this site. To investigate dietary patterns in the Three Kingdoms period, we compared our results with reported isotopic data from other southeastern Three Kingdoms sites (Imdang‐dong, Songhyeon‐dong and Yean‐ri). We found that the Sunhung individuals had similar isotope ratios to the people from these other sites. However, there was noticeable isotopic difference among individuals from each study site, although much of the dietary protein in each site was mainly from terrestrial sources. We propose that the most parsimonious explanation for this isotopic pattern is variation in social status during this time period. Copyright © 2012 John Wiley & Sons, Ltd.