The aim of this work was to analyse the diet of a Merovingian population sample of 80 individuals buried at Norroy-le-Veneur, France, with regard to their social status and chronology. A carbon and nitrogen stable isotope analysis of human adult bone collagen and related fauna from the same cemetery showed a diet based primarily on C3 plants, supplemented with animal protein in a range comparable to other contemporary sites. No significant contribution of C4 plants (e.g. millet) or marine-derived protein was detected. In terms of socio-economic stratification, individuals buried with rich grave good assemblages formed a narrow group with a significantly higher mean of δ13C than low-ranking individuals. We argue that this may represent a step in the gradual formation of the dietary exclusivity of Frankish elites, following a progressive rise in power of the Merovingian nobility. Also, during the timespan of the cemetery there was a population-wide decrease of 0.3 ‰ in the mean value of δ13C. The role of the Christian conversion of the population is questioned, but another factor influencing diet might have played a role.