A 2-yr-old male captive timber wolf, kept in an outdoor enclosure in Austria, presented with anorexia, depression, and fever in June. Tick infestation was reported despite monthly acaricidal treatment. The microscopic examination of a blood smear revealed elementary bodies and morulae suspicious for Anaplasma phagocytophilum. Polymerase chain reaction confirmed the infection by the G-variant of the pathogen, also found in horses and humans but not in wild ruminants. The wolf seroconverted within 2 wk, and antibodies persisted thereafter. Therapy was started with doxycycline for 10 days, and the wolf recovered within 24 hr. Clinical symptoms and temporary changes in blood parameters (thrombocytopenia, lymphopenia, mild anemia) in this wolf show high similarity to granulocytic anaplasmosis seen in dogs. This is the first report on granulocytic anaplasmosis in a wolf, indicating that A. phagocytophilum might cause clinical disease in the wolf.