A new electroless Ni-B coating, whose formulation is not available commercially, is developed. After doing successful Ni-B coating, nano size diamond particles (UDD-Ultra dispersive diamond) are added to improve hardness and wear resistance properties of the coating. Five different suspensions are prepared and also five different electroless composite Ni-B coatings are obtained. Deposition thicknesses, rates and the microhardness of coatings after in as-plated and heat-treated conditions are measured. The better composite coatings are chosen and then wear test (ball on plate) is done to the nano composite coatings, electroless Ni-B coating and uncoated plain carbon steel. The evaluation of experimental results is done. Microhardness of the coating greatly increased because of the presence of the nanoparticles. The hardest electroless composite coating (1250 HV100) is 30 times more resistant to wear than steel material, 14 times than electroless Ni-B coatings.