The invention provides novel biparatopic LRP5/LRP6 cross-reactive binding polypeptides, and more specifically novel biparatopic LRP5/LRP6 cross-reactive immunoglobulin single variable domain constructs which can inhibit Wnt signaling pathways. The invention also relates to specific sequences of such polypeptides, methods of their production, and methods of using them, including methods of treatment of diseases such as cancer.