Iron deficiency was absent in a recent population assessment of rural Bangladeshi women exhibiting anemia (57%), suggesting other causes of low hemoglobin. We assessed the relative influence on anemia of thalassemia, groundwater arsenic and iron, and diet among women of reproductive age living in rural Bangladesh. Women (n=207) sampled from a previous antenatal nutrient intervention trial in rural Bangladesh were visited during two seasons in 2008. Collected data included 7-day dietary and 24-hour drinking water intake recalls, 7-day morbidity recall, anthropometry, and drinking water arsenic and iron concentrations. Capillary blood was analyzed for iron (plasma ferritin, soluble transferrin receptor), inflammation (C-reactive protein) and thalassemia (β thalassemia and Hb E) status. In stratified, adjusted analyses, only parity was associated with anemia (odds ratio, OR (95% CI): 11.34 (1.94, 66.15)) for those with thalassemia (28% prevalent). In contrast, groundwater iron intake (>30 mg/d, 0.48 (0.24, 0.96)) and wasting (2.32 (1.17, 4.62)) were associated with anemia among those without thalassemia. Elevated groundwater arsenic (>50 μg/L, 12% of tubewells) and a diverse diet were unrelated to anemia regardless of thalassemia diagnosis (p>0.70 and >0.47, respectively). Among women in this typical rural Bangladeshi area, the prevalence of thalassemia was high and, unlike iron deficiency which was absent most likely due to high iron intake from groundwater, contributed to the risk of anemia. In such settings, the influence of environmental sources of iron and the role of thalassemias in contributing to anemia at the population level may be underappreciated.