Incarcerated and detained persons are at increased risk for acquiring COVID-19. However, little is known about their willingness to receive a COVID-19 vaccination. During September-December 2020, residents in three prisons and 13 jails in four states were surveyed regarding their willingness to receive a COVID-19 vaccination and their reasons for COVID-19 vaccination hesitancy or refusal. Among 5,110 participants, 2,294 (44.9%) said they would receive a COVID-19 vaccination, 498 (9.8%) said they would hesitate to receive it, and 2,318 (45.4%) said they would refuse to receive it. Willingness to receive a COVID-19 vaccination was lowest among Black/African American (Black) (36.7%; 510 of 1,390) persons, participants aged 18-29 years (38.5%; 583 of 1,516), and those who lived in jails versus prisons (43.7%; 1,850 of 4,232). Common reasons reported for COVID-19 vaccine hesitancy were waiting for more information (54.8%) and efficacy or safety concerns (31.0%). The most common reason for COVID-19 vaccination refusal was distrust of health care, correctional, or government personnel or institutions (20.1%). Public health interventions to improve vaccine confidence and trust are needed to increase vaccination acceptance by incarcerated or detained persons.