Thirty million Bangladeshis continue to drink water with unacceptable levels of arsenic (>10 μg/L), resulting in a large public health burden. The vast majority of the Bangladeshi population relies on private wells, and less than 12% use piped water, increasing the complexity of mitigation efforts. While mass testing and informational campaigns were successful in the early 2,000 s, they have received little attention in recent years, even though the number of wells in the country has likely more than doubled. We investigated the effect of a low-cost (<USD 10/household) informational intervention on reducing arsenic exposure through a randomized control trial design. The sample size was ∼10% of the study area households, and the intervention provided exposure awareness material, the arsenic concentration of the household's drinking water, and information about alternate water sources nearby with improved water quality. The informational intervention lowered household arsenic exposure (P = 0.0002), with an average reduction in arsenic levels of ∼60%. Approximately one third of the study households requested to test an additional water source at no cost. Providing the intervention a second time led to more households changing their water source but did not further reduce exposure (P = 0.39). Our study establishes a causal relationship between the informational intervention and the observed reduction in household arsenic exposure. Our findings demonstrate that water testing and recommendations for accessing improved water provide an immediate, effective, and inexpensive means of reducing the public health burden of arsenic exposure in Bangladesh.