Strong increase in electrical conductivity of graphene oxide (GO) (I a parts per thousand 10(-9) A) is found by addition of Ni nanoparticles (Ni-NPs) preliminarily solved by HCl (Ni-sol) (I a parts per thousand 10(-4) A) or powder (Ni-pow) obtained from this solution (I a parts per thousand 10(-6) A), while simply mixing GO with Ni-NPs an insulator similar to pure GO is obtained. Thus, Ni-sol and Ni-pow can be used to transform GO from insulator to semiconductor. One of the transformation mechanisms is Ni as spillover. At the same time, different kinds of the magnetic response are obtained on GO and reduced GO (rGO) samples with and without Ni. Weak paramagnetic response is detected in pure GO. Stronger paramagnetic behavior is observed for GO and rGO mixed with Ni-sol or Ni-pow. Pure rGO sample shows weak ferromagnetism represented by slim but visible hysteresis with remnant magnetization M (r) of 0.05 emu/g. GO with Ni-NPs presents clear hysteresis with M (r) of 2.8 emu/g, while sample prepared by addition of Ni-NPs to rGO presents the largest hysteresis with M (r) as high as 11.8 emu/g. Thus, the optimal procedure to obtain the magnetic response requested for particular application can be chosen.