Quartz crystal microbalance experiments were performed to study the kinetics of surface adsorption from solutions containing oppositely charged nanoparticles. A theoretical model was developed according to which formation of dense nanoparticle (NP) monolayers is driven by a cooperative process, in which the already-adsorbed NPs facilitate adsorption of NPs from solution. The kinetic rate constants change with the NP solution concentration and can be used to backtrack adsorption free energies. These energies agree with the predictions of a simple DLVO model.