Individual dietary differences (e.g. sex, age, period, and region) among townspeople during the Edo period are unclear, although the historical literature describes the general dietary menu. We applied carbon and nitrogen stable isotope analyses to 103 adult human skeletons excavated from the Ikenohata-Shichikencho site of the Edo period (late 17th to late 19th century AD) in Japan to investigate individual dietary differences among townspeople in the city of Edo. The mean carbon and nitrogen isotope ratios of Ikenohata townspeople were −19.7 ± 0.4‰ and 10.8 ± 0.7‰, respectively, which suggests that C₃-based terrestrial foods, freshwater fish, and marine fish were their main dietary protein sources. Intra-population comparisons indicated no significant difference among individuals of different sexes, age categories, and chronological periods, with the exception of a sex difference in carbon isotope ratios (0.37‰) during the Middle–Late period (last half of 18th century). Comparison of the Ikenohata data with the results of previous studies revealed significant isotopic differences in skeletal populations of the same social class (up to 1.33‰ for nitrogen) and same Edo city (up to 1.64‰ for nitrogen). Although these differences were relatively small in terms of stable isotope ecology, dietary food sources for people during the Edo period would differ to some extent by their social class and geographic region of residence.