This study provides morphological descriptions of three distinct types of hemocytes and one type of oenocyte newly observed in the body cavity of several freshwater ostracode species (Candona candida, C. neglecta, Herpetocypris reptans, H. incongruens, Eucypris virens, Psychrodromus olivaceus, Notodromas monacha, N. persica and Scottia birigida, all Podocopida, Cypridoidea). These cells were found in both males and females and in both juveniles and adults predominantly in inter-lamellar space, along the dorsal margin of the body cavity and in the anteroventral part of the body cavity. In TEM, large granulocytes with a number of pseudopodia and remarkable rounded granula were observed. Their affinity to muscle syncytia and a role in phagocytosis of exogenous particles is distinct. Oenocytoid-like cells with homogenous cytoplasm, rich in polyribosomes and with few membrane-delimited vesicles, were caught in the peripheral parts of body cavity accumulating in special multicellular formations. The oenocytoid-like cells were observed in two cases also by light microscopy. Two types of plasmatocytes (agranular and granular) with numerous pseudopodia were observed in TEM to be involved in phagocytosis of cell debris. Moreover, the plasmatocytes are located in close vicinity with the multicellular formations of oenocytoid-like cells and envelope them or form a sheath. Oenocytes were shown by light microscopy using histological staining to occur in huge amounts in juveniles. In adults their frequency becomes considerably lower. Possible functions of these cells are discussed in the context of invertebrate haematology, physiology and immunology.