Four types of granulocytes, neutrophil, basophil, eosinophil and pithy granulocyte, were observed in peripheral blood of bowfin Amia calva. The neutrophil had three types of granules, eosinophilic granule (αG； orange), chromophobic granule (βG) and basophilic granule (γG； light blue) in the cytoplasm. These granules were round or oval, but the maximum diameter was different each other (αG, ≤0.5 μm; βG, ≤1.0 μm； γG, ≤0.3 μm). Alkaline phosphatase and peroxidase (PO) were detected in the βG, however, central part of the granule was negative. Basophil had round or oval granules (≤1.1 μm) which show violet. The granules were periodic acid Schiff (PAS) and toluidine blue (TB) positive. Eosinophil had two types of granules. One was major which was large and showed eosinophilic, another was minor with small size and basophilic. Both granules were PO positive (the former was weakly and the latter strongly). The latter was also PAS and TB positive. Pithy granulocyte was occasionally found in the blood. The granulocyte had ovoid granules with eosinophilic rod-shaped core and chromophobic surrounding part of the core.