The nickel matrix has a significant impact on the structure and performance of a nickel–metal hydride (NiMH) battery. However, few studies have focused on the nickel matrix thus far due to the difficulty of fabricating controllable porous nickel materials. In addition, conventional nickel matrices show poor flexibility, making it difficult to fabricate flexible NiMH batteries. To achieve a high performance flexible NiMH battery, the fabrication of a thin, free-standing, and flexible nickel matrix with an optimized pore structure is a key prerequisite. Here, a novel flexible porous nickel matrix with a controllable pore size, density, and distribution of pore position is developed by nickel electrodeposition on templates that are produced by silkscreen printing different insulating ink microarrays on stainless steel sheets. Benefitting from the excellent structure of the porous nickel matrix, flexible NiMH batteries are fabricated, which show excellent flexibility and very high energy densities of 151.8 W h kg−1 and 508.5 W h L−1 as well as high energy efficiencies of 87.9–98.5%. These batteries outperform conventional NiMH batteries and many other commercial batteries, holding great promise for their future practical application. The present strategy provides a new route to promote the development of nickel-based alkaline rechargeable batteries.