A white-yellowish 5-7 cm sized solid mass was observed in the mammary gland of a 7 years old poodle bitch. Mass was well-defined and metastasis was not observed. In microscopic findings, mass contained hyperplasia of glandular epithelial cells, proliferation of mucin-secreting myoepithelial cells and their stroma and formation of cartilage and bone. Bone marrow with fat and hematopoietic cells was observed. Based on the microscopic findings, the mass was diagnosed as benign mixed tumor of the mammary gland in dog.