Double-shelled Ag/C/Ni nanocables have been synthesized through a deposition covering process of Ni nanoparticles (NPs) onto Ag/C pentagonal prism nanowires (NWs). The proposed synthesis mechanism is corroborated by scanning electron microscopy, transition electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-vis absorption spectroscopy. The resulting Ag/C/Ni nanocables with an average diameter of ∼270 nm are made up of Ag NW core (∼200 nm diameter) with internal amorphous C layer (∼10 nm thickness) and outer Ni shell (∼25 nm thickness). The UV-vis absorption spectroscopy analysis indicates that the covering of the Ni shell on the Ag/C nanowire can dampen the surface plasmon resonance (SPR) of Ag wire core and lead to a red-shifted SPR absorption peak. In particular, compared with Ni NPs, the resultant double-shelled Ag/C/Ni magnetic nanocables exhibits higher catalytic activity for the dehydrogenation toward aqueous ammonia borane under ambient atmosphere, and its calculated activation energy is lower than those of many bimetallic catalysts.