Improving maternal nutrition is an important step toward reducing low birth weight (LBW) and its sequelae. In India, an estimated 7.5 million babies are born each year with LBW, which accounts for more than one-third of the global burden. In this context, little is known about the population-level association of iron and folic acid supplementation (IFA) during pregnancy and reducing the outcome of LBW. Using pooled data from the nationally representative 1998/1999 and 2005/2006 National Family Health Surveys of India, we examined the association of IFA with LBW and birth weight using multivariable logistic and linear regression models, respectively (n = 22,648). We found that IFA during pregnancy was negatively associated with LBW after adjustment for socioeconomic status [OR = 0.77 (95% CI: 0.68, 0.87); P < 0.001] and further adjustment for antenatal care (ANC) utilization [OR = 0.82 (95% CI: 0.72, 0.94); P < 0.001]. This corresponded to a 41-g [(95% CI: 2 g, 80 g); P < 0.05] increase in birth weight, which attenuated to 28 g [(95% CI: -12 g, 68 g); P = 0.71] after additional adjustment for ANC. At the population level in a context where the burden of anemia is severe (prevalence ≥40%), IFA during pregnancy was significantly associated with decreased LBW. Measures to improve the implementation of this simple intervention should help to address India's burden of LBW.