In April 2004, the Colorado Department of Public Health and Environment (CDPHE) was notified about a boy aged 3 years with diagnosed tularemia associated with a hamster bite. Tularemia has not been associated previously with pet hamsters. CDPHE conducted an investigation to determine whether other owners of hamsters were at risk. Clinicians and public health officials should be aware that pet hamsters are a potential source of tularemia.