In this work, Boron-doped B-x:Ni/NiO delta [x(%) = 0.0, 5.0, 10.0 and 15.0] core/shell magnetic nanoparticles were synthesized by the polyol reduction process. The XRD spectra of the samples indicate that the B addition does not cause any change in the cubic structure of Ni. The TEM photographs present that nanoparticle formation and accumulation orientation occurs in various shapes as spherical, octahedral-like and octopus-like accumulation. The average particle sizes of B-x:Ni/NiO(delta)MNPs forx(%) = 0.0, 5.0, 10.0, 15.0 were found as similar to 90, 12, 46, 5 nm, respectively, from the TEM images. It is observed from the temperature and magnetic field dependence magnetization measurements that magnetization of Ni/NiO delta core/shell MNPs increases with increasing Boron concentration from 5 to 15%. One can be deduced that this increment in the magnetization comes from the resulting of strengthening the Ni-B ferromagnetic interaction. The highest saturation magnetizations under 1 T magnetic field were found as similar to 37 and similar to 30 emu/g at 10 and 300 K, respectively.