Background/Aim: Exposure to arsenic during childhood is associated with adverse health problems including cancers and non-cancerous diseases. However, little is known about its effect on vaccine-related humoral immunity in children. In this study, we examined the association between arsenic exposure and measles antibody titers in US children. Methods: The association between urinary arsenic and serum measles antibody levels in the US children aged between 6 and 11 was investigated, based on the National Health and Nutrition Examination Survey (NHANES) 2003-2004 and 2009-2010. The total urinary arsenic level was calculated by summing inorganic arsenic and their metabolites (arsenite, arsenate, methylarsonic acid, and dimethylarsinic acid), and was divided by the level of urinary creatinine. The generalized linear regression was conducted to evaluate the association, adjusted for the cycle, age, race, undergrowth, secondhand smoking, and poverty index ratio. Stratified analyses were conducted by gender and serum folate levels using the median as cutoff (18.7 ng/mL). Results: The level of serum measles antibody titers decreased by 28.1% (95%CI: −44.2%, −12.0%) per tertile increase in the concentration of creatinine-adjusted urinary arsenic among boys with serum folate levels lower than 18.7 ng/ml. However, no associations were observed in boys with high serum folate levels and girls. Conclusion: Our stratified analysis showed the inverse association between arsenic exposure and measles antibody level among boys with lower folate intake. This study will provide the basis for an intervention strategy to protect children’s health from arsenic exposure.