Morphological and cytochemical characteristics of leukocytes from gray mullet (Mugil cephalus) were examined by light microscopy. Lymphocyte, monocyte and neutrophil were observed in the peripheral blood. Lymphocyte had round to oval nucleus with coarse chromatin-mesh. Cytoplasm was agranular or contained some basophilic (blue) granules (Lymphocyte Basophilic Granule, LBG). Monocyte had round to kidney-shaped nucleus with fine chromatin-mesh and monocyte major granule (MMG) in the cytoplasm. Neutrophil were round to oval and the nucleus round to lobuleshaped. Only one type of granule, chromophobic granule (βG) was observed in the neutrophil. The βG was round to oval, unstained by Romanowsky type stain and peroxidase positive. The Yasumoto body was also found in the neutrophil and toluidine blue positive (orthochromatically).