In this work, ruthenium nanoparticles were immobilized on thiol-based dendrimer functionalized nano-silica and its catalytic activity was investigated in the oxidation reactions. To do this, silica nanoparticles were functionalized with a thiol-based dendrimer, and this dendritic material was used as a host for immobilization of ruthenium nanoparticles as guest species. Different analytical tools such as FT-IR and UV-vis spectroscopies, CHNS, ICP and TGA analyses, and TEM and SEM microscopic techniques were used to characterize the prepared catalyst. The catalytic activity of this nanocomposite material as a heterogeneous catalyst was studied in the epoxidation of alkenes and oxidation of alcohols with tert-butyl hydroperoxide (tert-BuOOH) and the corresponding products were obtained in good to excellent yields. Moreover, this catalyst can be well-dispersed in the reaction medium, conveniently separated from the reaction mixture, and reused several times without significant loss of its activity. Ru-np-nSTDP provided a highly stable, active, reusable, and solid-phase catalyst for preparation of a series of epoxides and aldehydes. [GRAPHICS] .