We estimate the effect of county-level e-cigarette indoor vaping restrictions (IVRs) on infant mortality using United States birth certificates from 2010 to 2015. We estimate difference-indifferences models and find that e-cigarette indoor vaping restrictions increased infant mortality by 0.39 infants per 1,000 live births (12.9%). These effects were disproportionately higher for infants born to younger mothers and in locations with higher baseline levels of prenatal smoking. Infant mortality increased by 34.1% between 100 days to 1 year after IVRs. Infant mortality due to infections and neoplasms were particularly elevated.