Pd(0) nanoparticles (NPs) decorated on graphene nanosheets (GNS), Pd/GNS, have been synthesized by classical wet-chemical method and reduced by using sodium borohydride. The definition of the Pd/GNS nanocatalyst by the combination methods reveals that the formation of well-dispersed highly crystalline 3.68 +/- 0.35 nm Pd(0) NPs on the surface of GNS. The Pd/GNS nanocatalyst was tested as a catalyst in the hydrogen production reaction via methanolysis of ammonia-borane. Compared with the heterogeneous catalyst systems used for this reaction up to now in the literature, it has been understood that this is one of the best catalysts in terms of high efficiency (TOF = 101.5 mol H-2 mol catalyst(-1) min(-1), 253.75 min(-1) corrected for the surface atoms), low activation energy (46 kJ mol(-1)) and total conversion (> 99%) at room conditions. The more important is the remarkable stability of Pd/GNS against to agglomeration make Pd/GNS recyclable catalyst for the methanolysis of AB. Pd/GNS nanocatalyst retains 74.6% of its initial activity with 95.8% of conversion even at 5(th) recycle in the methanolysis of AB. Finally, the methanolysis reaction was carried out at various temperatures with different catalyst and substrate concentrations to write the rate equation and determine other activation parameters (Delta H-# and Delta S-#).