Perovskite solar cells (PSCs) represent a pivotal change in photovoltaics and are emerging as one of the most promising solar cell technologies for highly efficient and cost-effective solar energy production. In PSCs, the hole transport layer (HTL) plays a significant role in achieving high efficiency by improving charge collection and reducing recombination losses at the interface of the HTL/perovskite. Herein, we present a detailed investigation of the photovoltaic performance of PSCs by employing Fe-doped NiOx nanoparticles (NPs) as HTL. A simple solution method is adopted to synthesize Fe-doped NiOx NPs and their corresponding films are deposited by spin coating using Fe-NiOx inks at room temperature without any post treatment. As the obtained Fe-doped NiOx films exhibited an improvement in conductivity and work function, they resulted in an improvement in hole extraction and charge collection, while suppressing the charge recombination. Consequently, Fe-NiOx-based devices provided a significant enhancement in power conversion efficiency (PCE) of 17.57% compared to pristine NiOx of 15.41%. Flexible PSCs also showed an improvement in PCE from 13.37% for pristine NiOx to 14.42% for Fe-NiOx NPs. This work demonstrates that Fe-doped NiOx can be a promising HTL for fabricating highly efficient and flexible PSC production in the future.