U.S. employers can check whether the workers they hire are legally eligible for employment using E-Verify, a free electronic system run by the federal government. We use confidential data from the U.S. Department of Homeland Security to provide the first examination of whether increases in employer enrollment in the E-Verify system affect employment and earnings among workers who are particularly likely to be unauthorized, namely Hispanic non-naturalized immigrants who have not completed high school, and their U.S.-citizen counterparts. We find evidence of negative effects on likely unauthorized immigrant men but positive effects on women. These results are robust to instrumenting for endogenous employer enrollment with state laws that require some or all employers to use the E-Verify system. The results are consistent with a household model of labor supply among unauthorized immigrants.