A NiOx−graphene oxide (NiOx−GO) hybrid has been prepared by a simple solution-processed method and was used as hole-extraction material in perovskite solar cells with either gold or carbon as back contact electrode. The impact of GO content on the optoelectronic behavior of NiOx and the photovoltaic performance of the fabricated devices has been studied. Thus, GO incorporation showed a significant improvement in the performance of NiOx-based devices. The best attained efficiency was 13.3%, and it was 45% higher than that with pure NiOx. This is attributed to a significant improvement in the hole extraction, recombination resistance, and energy-level matching in comparison to pure NiOx. In addition, NiOx−GO/Au-based perovskite solar cell devices showed a negligible hysteresis effect and high reliability and repeatability. When carbon was used as back contact electrode, the obtained efficiencies were lower, but it leaves space for improvement. Devices based on inorganic hole transporters NiOx or NiOx−GO demonstrated higher stability in ambient air compared to a standard cell based on spiro-OMeTAD.