Nickel nanoparticles are obtained by electrical explosion of wire under the action of a high-voltage discharge followed by condensation in an inert gas medium. When butane is added to the gas medium, a carbon shell is deposited onto the condensing nickel particles. Immediately after the synthesis, liquid-phase modification of nanoparticles is carried out with aqueous solutions of polysaccharides agarose and gellan. As a result, a polymer shell is formed on particles of Ni and nickel particles coated with a carbon shell (Ni@C). The dispersity, crystalline structure, and magnetic properties of Ni and Ni@C nanoparticles are characterized by transmission microscopy, X-ray diffraction analysis, and vibration magnetometry. The total carbon content on the surface of the nanoparticles is determined by thermal analysis with simultaneous mass spectrometry. It is shown that, under the studied conditions, polysaccharides are deposited onto the nanoparticles in amounts up to 2 wt % to form a shell with a thickness of about 4 nm. When agarose is used as a modifier, the content of the polysaccharide increases with the concentration of the modifying solution. When gellan is used as a modifier, a more complex concentration dependence is observed: an initial increase is followed by a decrease in the amount of deposited polysaccharide. The results are discussed from the viewpoint of the influence of the molecular weight of a polymer on the adsorption process. [Figure not available: see fulltext.]