Mercury (Hg) isotopic signatures were characterized in polished rice samples from China, U.S., and Indonesia (n = 45). Hg isotopes were also analyzed in paired hair samples for participants from China (n = 21). For the latter, we also quantified the proportion of methylmercury intake through rice (range: 31-100%), and the weekly servings of fish meals (range: 0-5.6 servings/weekly). For these participants, 29% (n = 6) never ingested fish, 52% (n = 11) ingested fish < twice/weekly, and 19% (n = 4) ingested fish >= twice/weekly. In rice and hair, both mass-dependent fractionation (MDF, reported as delta Hg-202) and mass-independent fractionation (MIF, reported as Delta Hg-199) of Hg isotopes were observed. Compared to rice, hair delta Hg-202 values were enriched on average (+/- 1 standard deviation) by 1.9 +/- 0.61 parts per thousand, although the range was wide (range: 0.45 parts per thousand, 3.0 parts per thousand). Hair Delta Hg-199 was significantly inversely associated with %methylmercury intake from rice (Spearmans rho = -0.61, p < 0.01, n = 21), i.e., as the proportion of methylmercury intake from rice increased, MIF decreased. Additionally, hair Delta Hg-199 was significantly higher for participants ingesting fish >= twice/weekly compared to those who did not ingest fish or ingested fish < twice/weekly (ANOVA, p < 0.05, n = 21); Overall, results suggest that Hg isotopes (especially MIF) in human hair can be used to distinguish methylmercury intake from rice versus fish.