In this work, self‐supporting three‐dimensional hierarchical nanostructured MoS 2 @Ni(OH) 2 nanocomposites are synthesized via a facile single‐mode microwave hydrothermal technique. The fabricated MoS 2 @Ni(OH) 2 nanocomposites for supercapacitors in aqueous electrolyte exhibit higher specific capacitance and better cyclic stability than those of MoS 2 and Ni(OH) 2 due to the pronounced synergistic effect between MoS 2 and Ni(OH) 2 . Further, the flexible all‐solid‐state supercapcitor is readily constructed by composing the PVA/KOH gel electrolyte in between two MoS 2 @Ni(OH) 2 electrodes on the flexible PET substrates. The resulting supercapacitors can operate at high rate up to 1000 V/s, have excellent long‐life cycling stability, retaining 94.2% of the initial capacitance after 9000 cycles, and mechanical flexibility during extreme bending, respectively. Thereby, the MoS 2 @Ni(OH) 2 nanocomposites are a promising electrode materials for flexible long‐life cycling all‐solid‐sate supercapacitors.