Colloidal suspensions of ruthenium nanoparticles (Ru0 NPs) stabilized by randomly methylated β-cyclodextrins were easily prepared in aqueous solution by two comparative reductive approaches. The first method relies on a one-step hydrogen reduction of ruthenium trichloride as a metal precursor in the presence of cyclodextrins (one-pot method). The second method consists of the chemical reduction of metal salts by NaBH4, followed by the stabilization of ruthenium NPs by post-addition of the methylated β-cyclodextrins (cascade method). The modified β-cyclodextrin-capped ruthenium NPs obtained were characterized using TEM, DLS, and NMR techniques. The highly dispersed colloidal suspensions contain very small particles in the size range of 1–1.4 nm. Their catalytic performances were investigated in terms of activity and selectivity of their biphasic hydrogenation of various substrates (olefins, ketones, and disubstituted arenes) under mild conditions.