Purpose To analyze the differential rural‐urban impacts of the Affordable Care Act Medicaid expansion on low‐income childless adults’ health insurance coverage. Methods Using data from the American Community Survey years 2011‐2015, we conducted a difference‐in‐differences regression analysis to test for changes in the probability of low‐income childless adults having insurance in states that expanded Medicaid versus states that did not expand, in rural versus urban areas. Analyses employed survey weights, adjusted for covariates, and included a set of falsification tests as well as sensitivity analyses. Findings Medicaid expansion under the Affordable Care Act increased the probability of Medicaid coverage for targeted populations in rural and urban areas, with a significantly greater increase in rural areas (P < .05), but some of these gains were offset by reductions in individual purchased insurance among rural populations (P < .01). Falsification tests showed that the insurance increases were specific to low‐income childless adults, as expected, and were largely insignificant for other populations. Conclusions The Medicaid expansion increased the probability of having “any insurance” for the pooled urban and rural low‐income populations, and it specifically increased Medicaid coverage more in rural versus urban populations. There was some evidence that the expansion was accompanied by some shifting from individual purchased insurance to Medicaid in rural areas, and there is a need for future work to understand the implications of this shift on expenditures, access to care and utilization.