A direct temporal measurement of the internal motion of a host-guest bimolecular complex is reported. Time-resolved polarization spectroscopy is used to monitor the motion of a guest chromophore, anthracene-1,3-dicarboxylate, bound to a bis(guanidinium) host molecule through a combination of hydrogen bonding and electrostatic forces. The dynamics of the bound chromophore is well described by an overdamped oscillator model. Through simple modeling, it is possible to estimate the frequency of the host-guest potential and the range of the guest chromophore＇s angular displacement.