We have investigated magnetic properties of the selected nanoparticles (nanoparticles of the nickel-cobalt-boron, NiCoB, alloy, uncoated and coated with SiO2 and nanoparticles of nickel, Ni, coated with carbon) and electromagnetic properties of the superconducting magnesium diboride, MgB2, wires, undoped and doped with these nanoparticles. Uncoated and coated NiCoB nanoparticles are in an amorphous state and size of the particles is 15 − 20 nm. Relaxation time of magnetization of the NiCoB particles is longer than time of the measurement of magnetization at low temperature. The magnetic behaviour of the particles is described within the model of singledomain particles with thermal activation of the magnetic moment of the particle over the anisotropy barrier. Superparamagnetic behaviour of the particles at room temperature, relatively high magnetization at low temperature and in high field, as well as relatively small coercive field of the selected particles (NiCoB i Ni) are favourable for magnetic pinning of the magnetic vortices in superconductor. Electromagnetic properties of the MgB2 doped with magnetic particles are the result of the competition of the negative influence of the magnetic particles inside superconductor and enhancement of the flux pinning, which is achieved by nanoparticle doping. Although transition temperature, Tc, is lower in doped samples, higher values of the critical current density, Jc, are achieved in doped samples at low temperatures and high filed region. At low field region, the irreversibility field, Birr of the samples doped with Ni nanoparticles is enhanced with respect to undoped sample, which can be related to the flux pinning enhancement via attractive magnetic interaction between particles and vortices in superconductor.