STUDY OBJECTIVE: Emergency departments (EDs) often serve vulnerable populations who may lack primary care and have suffered disproportionate COVID-19 pandemic effects. Comparing patients having and lacking a regular source of medical care and other ED patient characteristics, we assessed COVID-19 vaccine hesitancy, reasons for not wanting the vaccine, perceived access to vaccine sites, and willingness to get the vaccine as part of ED care. METHODS: This was a cross-sectional survey conducted from December 10, 2020, to March 7, 2021, at 15 safety net US EDs. Primary outcomes were COVID-19 vaccine hesitancy, reasons for vaccine hesitancy, and sites (including EDs) for potential COVID-19 vaccine receipt. RESULTS: Of 2,575 patients approached, 2,301 (89.4%) participated. Of the 18.4% of respondents who lacked a regular source of medical care, 65% used the ED as their usual source of health care. The overall rate of vaccine hesitancy was 39%; the range among the 15 sites was 28% to 58%. Respondents who lacked a regular source of medical care were more commonly vaccine hesitant than those who had a regular source of medical care (47% versus 38%, 9% difference, 95% confidence interval 4% to 14%). Other characteristics associated with greater vaccine hesitancy were younger age, female sex, Black race, Latinx ethnicity, and not having received an influenza vaccine in the past 5 years. Of the 61% who would accept a COVID-19 vaccine, 21% stated that they lacked a primary physician or clinic at which to receive it; the vast majority (95%) of these respondents would accept the COVID-19 vaccine as part of their care in the ED. CONCLUSION: ED patients who lack a regular source of medical care are particularly hesitant regarding COVID-19 vaccination. Most COVID-19 vaccine acceptors would accept it as part of their care in the ED. EDs may play pivotal roles in COVID-19 vaccine messaging and delivery to highly vulnerable populations.