A captive colony of Brazilian free-tailed bats (Tadarida brasiliensis) was vaccinated with a commercial monovalent inactivated rabies virus (RABV) vaccine (RABVAC 1). Baseline rabies virus neutralizing antibodies (VNA) and the response to vaccination were measured in 50 bats. Rabies VNA was detected in the plasma of 64% (27/42) of bats that had been vaccinated 1 yr prior, but only 19% (8/42) had levels considered adequate. Rabies VNA was detected in the plasma of 63% (5/8) of bats with no record of previous vaccination, suggesting natural RABV exposure before captivity. All bats demonstrated a VNA response by 10 days postvaccination, and baseline titer significantly predicted humoral response to vaccination. No adverse reactions to vaccination or clinical signs of RABV infection were observed in the bats during a 6-mo observation period. Annual vaccination may maintain immunity against RABV infection in captive colonies of bats.