In this study, 71 human individuals were subjected to stable carbon (δ13C) and nitrogen (δ15N) isotope analysis of bone collagen samples for the purpose of determining human dietary patterns in Lithuania during the Late Roman and Migration periods. More specifically, based on the isotopic data, the aim was to determine and evaluate any potential dietary differences between individuals on the basis of their sex, age, social status and place of residence during the periods in question. The results of this study suggest that there were isotopically clearly distinguishable dietary differences between individuals from different parts/regions of Lithuania. Also, statistically significant dietary differences (on the basis of δ15N values) between males and females were observed (although, when making the same sex-based isotopic comparisons at an individual site level, the same result was observed only among those from Marvelė cemetery). However, no statistically significant isotopic differences were detected between different social or age groups. Overall, these results give us one of the first glimpses into the types of dietary habits practiced by people in various parts of Lithuania during the Roman and Migration periods, which could also serve as a good starting point for future investigations into other dietary aspects in the territories and periods in question that still remain unknown.