The effects of adsorbed surfactant on the redispersion behavior and the reactivity of nanocrystalline magnesium oxide prepared by an aerogel route (AP-MgO) have been investigated. Aerosol OT and didodecyl dimethylammonium bromide were chosen as examples of an anionic surfactant and a cationic surfactant, respectively. The redispersion studies were mainly carried out in nonaqueous solvents. The surfactant-adsorbed AP-MgO nanoparticles disperse better in some solvents compared to the uncoated AP-MgO nanoparticles. Surfactant adsorption on AP-MgO was found to break up the nanocrystalline aggregates to a reasonable extent as evidenced by dynamic light scattering and visible spectroscopy. The surfactant-adsorbed AP-MgO nanoparticles possess reasonable reactivity compared to bare AP-MgO as illustrated by the destructive adsorption reactions of paraoxon (diethyl 4-nitrophenyl phosphate) and (2-chloroethyl) ethyl sulfide.