Rotational nonlinear energy sinks (NESs) have been proposed to mitigate the response of underlying primary structures subjected to shock loading. This type of NES, which is composed of a passive mass that is free to rotate, has the potential to be easier to realize and more compact than other types of NESs. Like other types of NESs, these devices engage in targeted energy transfer, which allows for the broadband transfer of energy from the primary structure to the NES where it can be rapidly dissipated. Additionally, these devices can couple the dynamics of the primary structure and facilitate the transfer of energy from lower modes to higher modes, where it can be dissipated at a faster rate. This paper experimentally investigates the performance of this type of NES by using the results from tests of a rotational NES attached to a small-scale two-story structure. For these experiments, a shock load is provided to the primary structure using a shake-table-produced impulse-like ground motion. Additionally, by varying the amplitude of the input ground motion, the energy dependency of the performance of these devices can be investigated. The results of these experiments show that this type of NES can attenuate the response of a structure by responding in a highly effective rotational mode.