A case of neutrophilic granulocytic sarcoma and a case of acute basophilic leukemia are described. The former was diagnosed in an 8-year-old Holstein cow with a large intrathoracic tumor mass (case 1), and the latter in a 14-month-old Holstein heifer with a rapid increase in white blood cell count (case 2). In case 1, the tumor mass was composed of agranular cells and more mature cells with eosinophilic granules staining positive for naphthol AS-D chloroacetate esterase (CAE) and macrophage, myeloid/histiocyte antigen (clone MAC387). In case 2, the tumor tissues consisted chiefly of myeloblastoid cells. However, differentiation to myelocytoid or metamyelocytoid cells was observed, and their intracytoplasmic eosinophilic granules were positive for tryptase (a marker for basophils and mast cells), but not for CAE (a marker for neutrophils and mast cells). Although reports of myeloid neoplasms are rare in cattle, as documented here, it is not difficult to diagnose them on the basis of histology, histochemistry and immunohistochemistry.