This research examines the diets and mobility of higher status individuals buried in the St. Mary's (Mariakirken) churchyard (1140 and 1248 AD), located in Bergen, Norway. Stable isotope data are used to explore the role that diets (preferential access, choice of foods) may have played in mitigating the negative impacts of rapid urbanization. Dietary reconstruction involved analysis of carbon (δ13C) and nitrogen (δ15N) stable isotope ratios from paired bone and tooth samples from St. Mary's individuals (N = 25). Oxygen isotope ratios (δ18O) were derived from analyses of tooth enamel carbonate to comment on individuals' origins and mobility (N = 26). Individual δ13C and δ15N collagen values indicate that St. Mary's individuals consumed variable diets, with some relying on marine animal protein almost exclusively, while others primarily consumed C3 plants or animals that consumed C3 plants as the main source of their dietary protein. δ18O ratios showed that some individuals originated outside of Bergen. Thus, the stable isotope evidence (δ13C and δ15N) indicates that diets of St. Mary's individuals were more varied, and in some cases, relied primarily on imported trade goods such as grain/grain fed animals, and marine resources. This reinforces the view that St. Mary's represented an affluent segment of the growing Bergen population, and that its members were heavily involved in trade. Oxygen isotopes show that some individuals spent time living outside of Bergen during childhood. These data suggest that diets were more variable within the St. Mary's sample than at contemporary Norwegian sites, and that the process of urbanization did not impact the people of Bergen in a unified way.