In this work, Nickel-Cobalt-Phosphorous (Ni-Co-P) ternary coating has been deposited by electroless technique on copper substrate from an acidic electroless coating bath. The effects of heat treatment on surface roughness, surface morphology, crystal orientation and effect on hardness for electroless Ni-Co-P coating have been studied. The as-deposited Ni-Co-P alloy with high Phosphorous content shows initiation of crystalline structure. For the coated samples, structural changes have been observed after heat treatment. Theprecipitation of the Ni₃P phase has been observed after heat treatment at 400˚C. Further increase in annealing temperature resulted in the formation of CoP and Ni₂P phases. The hardness of the electroless Ni-Co-P coating has been found to reach its maximum at 400˚C annealing temperature due to the precipitation of Ni₃P phase. Annealing at 400˚C caused a significant increase of the hardness of as-deposited coating from 701.3 VHN to 1154.6 VHN.