This study describes histological and immunohistochemical evaluation of 50 epithelial and mesenchymal tumors of psittacines that were found in the archives of the pathology departments of veterinary faculties at Utrecht University and Istanbul University Cerrahpasa. In each case, cellular morphological features, tumoral pattern and mitotic activity were evaluated histologically, and immunohistochemistry was performed by the streptavidin-biotin immunoperoxidase method using a panel of commercially available antibodies raised against pan-cytokeratin, vimentin, muscle-specific actin, desmin, smooth muscle actin and Factor VIII/von Willebrand Factor. The histological evaluation revealed that 30 epithelial tumors were squamous cell carcinoma (n: 20), renal adenocarcinoma (n: 3), basal cell carcinoma (n: 2), abdominal carcinoma (n: 2), uropygial gland carcinoma (n: 1), cloacal carcinoma (n: 1) and cholangiocarcinoma (n: 1). Out of the 50 tumors, 13 had a mesenchymal origin and were diagnosed as fibrosarcoma (n: 4), hemangioma (n: 3), hemangiosarcoma (n: 4) and leiomyosarcoma (n: 2). Histological diagnosis could not be made for 7 tumors, and they were evaluated as undifferentiated malignant tumors (UDMT). Two tumors diagnosed as fibrosarcoma and three tumors diagnosed as UDMT showed strong SMA staining and were re-diagnosed as leiomyosarcoma. In view of the IHC findings, two other UDMTs were re-diagnosed as fibrosarcoma and anaplastic carcinoma. Although only a limited number of antibodies were used in the control panel, they were useful in establishing a definite diagnosis in some cases.