Promising and highly novel catalysts based on ruthenium (Ru) supported on reduced graphene oxide were synthesized, characterized and tested for CO_x-free hydrogen generation by catalytic ammonia decomposition. Metal loading and amount of a pre-reducing agent clearly affect the catalytic properties of the final catalysts. A Ru loading higher than 2.5?wt% resulted in Ru particles of size higher than 5?nm, which were agglomerated, thus decreasing the amount of the most active sites (B5 type-sites) and therefore the ammonia conversion. Additionally, a graphene oxide (GO) hydrothermal pre-reduction with 2-chloroethylamine hydrochloride, led materials with a more ordered structure which is associated with a good electronic conductivity and, higher basicity. Optimal catalytic activity is achieved using a reducing agent/GO ratio of 5/3 (wt/wt) and a Ru loading of 2.5?wt%. Thus, 2.5Ru/10C-rGO catalyst resulted in excellent hydrogen (H₂) production from ammonia decomposition, with an ammonia conversion close to 96% and hydrogen production rate of 9.1 mmolH₂ g_cat^?1 min^?1 at 400?°C. Reduced graphene oxide proved to be a suitable support in the development of nanosized Ru catalysts being the optimal one highly active in CO_x-free hydrogen generation during more than 60?h of reaction, providing virtuous stability.