Protein expression and subcellular localization of E-cadherin, alpha-catenin, and beta-catenin in 8 feline mammary tumor cell lines were examined by western blot analysis and fluorescence immunocytochemistry. A low E-cadherin expression was observed in FNN-m cells. Furthermore, compared to other cell lines, two E-cadherin bands existed in FMC-p1 cells and were localized in the perinuclear region; distinct radial lines were observed in the cytoplasm. A low alpha-catenin expression was observed in FON-m cells, but there were no apparent abnormalities in its localization. In contrast, similar levels of beta-catenin expression and cytoplasmic localization were observed in all cell lines.