jats:pMetal oxide charge transport materials are preferable for realizing long‐term stable and potentially low‐cost perovskite solar cells (PSCs). However, due to some technical difficulties (e.g., intricate fabrication protocols, high‐temperature heating process, incompatible solvents, etc.), it is still challenging to achieve efficient and reliable all‐metal‐oxide‐based devices. Here, we developed efficient inverted PSCs (IPSCs) based on solution‐processed nickel oxide (NiOjats:subx</jats:sub>) and tin oxide (SnOjats:sub2</jats:sub>) nanoparticles, working as hole and electron transport materials respectively, enabling a fast and balanced charge transfer for photogenerated charge carriers. Through further understanding and optimizing the perovskite/metal oxide interfaces, we have realized an outstanding power conversion efficiency (PCE) of 23.5% (the bandgap of the perovskite is 1.62 eV), which is the highest efficiency among IPSCs based on all‐metal‐oxide charge transport materials. Thanks to these stable metal oxides and improved interface properties, ambient stability (retaining 95% of initial PCE after 1 month), thermal stability (retaining 80% of initial PCE after 2 weeks) and light stability (retaining 90% of initial PCE after 1000 hours aging) of resultant devices are enhanced significantly. In addition, owing to the low‐temperature fabrication procedures of the entire device, we have obtained a PCE of over 21% for flexible IPSCs with enhanced operational stability.</jats:p>