Canine granulocytic anaplasmosis is a disease diagnosed in many areas of the United States, with the highest prevalence reported in dogs in the upper midwestern, northeastern, and western states. It is also found in several European countries. Anaplasmosis can manifest with a wide range of clinicopathologic findings. A 20 wk old puppy was presented with physical examination and laboratory findings atypical of the disease. In addition to other signs, abdominal effusion was detected. Diagnostic evaluation confirmed that the puppy was positive for anaplasmosis. No morulae were found in peripheral white blood cells, but morulae were apparent in the white cells of the abdominal effusion. Leukopenia was observed, characterized by neutropenia, as opposed to the lymphopenia and eosinopenia typically seen with the disease. Blast cells were also seen in the peripheral blood, and reactive lymphocytes were noted in the bone marrow. The patient responded well to doxycycline therapy. All hematologic and physical abnormalities resolved.