Supramolecular synthesis, the "bottom-up" construction of higher-order structures from monomeric building blocks, represents a flexible approach for the generation of multivalent materials. Here, monovalent building blocks decorated with a single bioactive ligand were synthesized. In water, these supramolecular elements self-assemble into columnar polymers that display multiple ligands. The supramolecular effect on the binding affinity was evaluated by using an enzyme-linked lectin assay, and the self-assembled architecture exhibited a stronger inhibitory power than that of the monovalent bioactive ligand. This so-called self-assembling multivalency enables the rapid and flexible generation of multivalent polymers from monovalent building blocks.