The development of hole-transport layers (HTLs) that elevate charge extraction, improve perovskite crystallinity, and decrease interfacial recombination is extremely important for enhancing the performance of inverted perovskite solar cells (PSCs). In this work, the nanoporous nickel oxide (NiO x ) layer as well as NiO x thin film was prepared via chemical bath deposition as the HTL. The sponge-like structure of the nanoporous NiO x helps to grow a pinhole-free perovskite film with a larger grain size compared to the NiO x thin film. The downshifted valence band of the nanoporous NiO x HTL can improve hole extraction from the perovskite absorbing layer. The device based on the nanoporous NiO x layer showed the highest efficiency of 13.43% and negligible hysteresis that was better than the one using the NiO x thin film as the HTL. Moreover, the PSCs sustained 80% of their initial efficiency after 50 days of storage. This study provides a powerful strategy to design PSCs with high efficiency and long-term stability for future production.