Although reduced levels of the epithelial cell adhesion molecule E-cadherin are often associated with poorly differentiated breast cancers, recent studies show that expression of other cadherins such as N-cadherin, P-cadherin, and the mesenchymal cadherin-11 is actually elevated in invasive breast cancers and cell lines. Cadherin-11 is unique among cadherins in that it exists as two alternatively spliced forms that are expressed together in the same cell. We now show that expression of wild-type cadherin-11, with or without coexpression of the COOH-terminal truncated splice variant, promotes epithelial differentiation of the cadherin-negative SKBR3 cell line. Exogenous wild-type cadherin-11 association with and membrane recruitment of beta-catenin and p120 are unaffected by coexpression of the truncated variant. Cadherin-11-expressing cells exhibit modest changes in cell proliferation and no change in anchorage-independent growth. However, coexpression of wild-type cadherin-11 and the splice variant promotes a dramatic increase in the ability of SKBR3 cells and E-cadherin-positive MCF7 cells to traverse Matrigel-coated filters. Biochemical studies indicate that the truncated variant may be secreted from the cell and/or enter a detergent-insoluble compartment. These data suggest that the presence of the cadherin-11 splice variant promotes invasion of cadherin-11-positive breast cancer cells.