Molecular tweezers are dynamic devices that are able to switch from one conformation to another upon stimulation by an external trigger. In this work, we report a new water-soluble macromolecular carrier bearing a pH-responsive molecular tweezer, whose affinity for a substrate depends on the external pH. The conformational change of the switching unit was evidenced by H-1 NMR spectroscopy, and fluorescence studies conducted in aqueous media demonstrated the ability of the carrier to bind to substrates in a pH-dependent fashion.