NMR experiments probe protein dynamics across a broad range of time scales from nsec to sec and as such, NMR is the gold standard for discovering and analyzing dynamic allostery in proteins. The protein ensemble of states reconfigures upon ligand binding, and NMR alone can assess which residues have changed their motions and on what timescales. Amide hydrogen/deuterium exchange mass spectrometry (HDX-MS) also often reveals reconfiguration of the protein ensemble upon ligand binding, but the timescale of motions that are reflected in the HDX-MS experiment is more difficult to ascertain. A few allosteric proteins have now been studied by both NMR and HDX-MS allowing a direct comparison of the data from both methods revealing the complementarity of the results from these different experiments as well as information about the timescales of motion reflected in the HDX-MS results. The insights gained from comparing NMR and HDX-MS of small monomeric proteins enable a clearer interpretation of the allostery revealed by HDX-MS in larger protein complexes and assemblies that are not amenable to NMR.