Stable, efficient, and reusable catalysts for wastewater treatment, promoting the catalytic elimination of environmental pollutants remains a current challenge. This work shows a one-pot synthesize Ag nanoparticles (AgNPs) supported on reduced graphene oxide (rGO/Ag) as a nanocatalyst. Morphological control of AgNPs was achieved by adding NH4OH during the nucleation and growth processes leading to the spherical nanoparticles with average size of 9 ± 3 nm). Temperature increase promotes decrease of the oxygenated functional groups on rGO sheets, with an ID/IG = 0.57 at 300 °C. Catalytic activity of rGO/Ag was investigated through the catalytic hydrogenation of methylene blue (MB) and rhodamine B (RhB) in the presence of NaBH4 as a reducing agent. The proposed mechanism is based on the transfer of 2e- and 1H+ between the nanocatalyst and the dye molecules. Dyes adsorption on the catalyst is a rate-determining step and was accelerated by the rGO support. X-ray photoelectron spectroscopy analysis before and after successive catalytic cycles indicated that the catalyst integrity was maintained, with a slight decrease in the silver amount from 4.53 to 3.78 at%. The decolorization reaction followed the pseudo-first-order kinetics model for both dyes, and our results showed an efficiency of around 30% higher than similar methods.