--Background: several studies have attempted to characterize the origin of canine transmissible venereal tumor (CTVT). However, the participation of cancer stem cells (CSC) has not been reported. Objectives: herein we describe the expression patterns of CSC markers CD44, CD34, CD90, and CD133 in CTVT. Methods: Thirty-eight samples were selected and assessed through flow cytometry and immunohistochemistry. Results and Conclusions: Twenty-two tumors were classified as plasmacytoid and 16 as mixed. Almost all tumors showed high CD44 and low CD34 levels. CD133 and CD90 expression varied among tumors. Cytological groups did not differ in the proportion of CSC markers. Our results suggest that CSC subpopulations might participate in CTVT.