Due to their well-ordered and flexible composition and structure, metal–organic frameworks (MOFs) have been the focus of intense interest as multifunctional nanostructures for electrochemical energy storage systems (ESS). The chapter explores the basic engineering approaches that increase the potential of MOF-derived materials in flexible ESS, including metal-ion batteries such as lithium-ion, sodium-ion, and zinc-ion batteries and supercapacitors (SCs), by controlled constituent design and state-of-the-art nanostructuring techniques. Specific focus is laid on MOF-based nanostructured arrays, which, when grown on conductive and flexible substrates with or without binders, enable fast electron and ion transportation, accelerated reaction kinetics, and exposure of more active sites. These 3-D nanoarray electrodes preserve structural integrity under bending or twisting, this nanoarray provides more active sites during charge/discharge cycling and significantly improves the device’s specific capacity/capacitance. The chapter compares common substrates of MOF-based nanoarrays and addresses the crucial correlation between material composition, structure, and electrochemical activity. A systematic summary of MOF-based and derived nanostructures (NSs) such as metal selenides, oxides, nitrides, phosphides, sulfides, and nitrogen-doped carbons summarizes their performance and application prospects in flexible ESS. The chapter also presents the current technical challenges and viewpoints on the future growth of MOF-derived NSs. The chapter concludes with a discussion on current limitations and gives prospective strategies for the further growth of MOF-derived NSs for flexible ESS, to bridge current gaps and accelerate advances in next-generation energy storage technologies.