Nickel impregnated Pd/H-mordenite catalysts with different Ni contents were synthesised and tested for hydroisomerisation of n-decane with flow H-2 gas. The XRD analysis of the catalysts showed the decrease of intensity with increase in Ni addition. The average metal particle size, measured by TEM, is also increased by increasing the Ni loading up to 0.2 wt.% The acidity of the catalysts measured by TPD of ammonia revealed the ion-exchange of the some acid sites by Ni2+. The oxidation states of Pd and Ni were identified by XPS. The reducibility of H-mordenite supported Pd, Ni and Ni-Pd catalysts was studied by TPR. The catalytic activities of Ni containing and Ni free Pd/H-mordenite catalysts were studied and found that addition of Ni up to 0.2 wt.% over 0.1 wt.% Pd/H-mordenite, increased the n-decane conversion and isomerisation selectivity. As the Ni content exceeded 0.2 wt.%, the conversion and cracked products are found to decrease and increase. Further Ni containing Pd/H-mordenite showed increased sustainability and favoured the protonated cyclopropane (PCP) intermediate mechanism in n-decane isomerisation. It has been concluded that Ni impregnated Pd/H-mordenite showed good activity towards n-decane isomerisation where isomerized products mixture showed better octane number. (C) 2008 Elsevier B.V. All rights reserved.