Key Points Question Did health care use among undocumented residents change with increasing anti-immigrant rhetoric during the 2016 presidential campaign? Findings In this cohort study based on a single-center analysis of health care use among 20 211 adults and children, there was a 34.5% decrease in completed primary care visits among undocumented children and 43.3% decrease in completed primary care visits among undocumented adults between June 16, 2015 (the start of the Trump campaign for presidency, associated with an increase in anti-immigrant rhetoric), and May 31, 2018, which was significantly greater than patients in the Medicaid group. Meaning A significant decrease was noted in this cohort study in the use of primary health care services among a sample of predominantly undocumented patients compared with those in a Medicaid control group in the setting of rising anti-immigrant rhetoric associated with the 2016 presidential campaign.