Severe illness and mortality from coronavirus disease 2019 (COVID-19) are especially pronounced threats for people experiencing homelessness. COVID-19 vaccination access is correspondingly urgent for this population. Advocates, healthcare providers, and homelessness service providers have been conducting substantial vaccination outreach in places around the world. Systematic empirical research should support and inform these efforts. This study estimates COVID-19 vaccination rates and reasons for hesitancy among people experiencing homelessness in Sacramento, California, as of late September and early October 2021. Survey data (N= 283) estimate that 58% of people experiencing homelessness in Sacramento were fully vaccinated and 65% were at least partially vaccinated, but these estimates are likely upper bounds for the true population rates. Many unvaccinated people still planned to receive the vaccine, and concerns about safety and side effects were the most common reasons for hesitancy. Vaccination was more common for people using homelessness services at higher levels, but even frequent visits to drop-in centers were associated with higher vaccination rates among unsheltered people. This group was especially likely to have been vaccinated through outreach efforts, like pop-up vaccination clinics and street medicine teams. The study’s results hopefully inform ongoing vaccination efforts and contribute to a growing empirical literature on this urgent topic.