A fatal adenovirus infection is described in a wild-caught American kestrel (Falco sparverius). Predominate lesions were a moderate to severe hepatitis with diffuse single-cell necrosis of hepatocytes and a splenitis characterized by necrosis of cells surrounding the sheathed arteries. Pan-nuclear eosinophilic to magenta inclusion bodies were abundant within hepatocytes. Polymerase chain reaction was used to amplify a portion of the hexon gene from DNA extracted from the bird's liver and spleen. Sequence analysis showed that the adenovirus infecting this kestrel was the falcon adenovirus with a sequence homology of 99.5% to the isolate from the Northern aplomado falcon (Falco femoralis) variant and 98.6% homology to isolates from the taita (Falco fasciinucha) and orange-breasted falcons (Falco deiroleucus). This report expands the range of species of falcons that are susceptible to falcon adenovirus infection and disease. Given that this kestrel was recently wild caught and housed in isolation with other wild-caught kestrels, it is likely that the falcon adenovirus is present in wild populations of American kestrels.