Mesoporous nickel cobaltite (NiCo2O4) nanosheets are synthesized using cost effective, ultra fast and environmental friendly microwave assisted heating method followed by a post-calcining process of as-prepared precursors. XRD, XPS, BET, SEM, TEM and HRTEM methods are used to characterize nanosheets. The as-prepared nanosheets with thickness of around 2 nm possess many interparticle mesopores. The nanosheets have mesoporous structure, high specific surface area (111.15 m2 g-1), large pore volume (0.3033 cm3 g-1) and narrow pore size distribution (2.25-10 nm). The flexible supercapacitor working electrode of mesoporous NiCo2O4 nanosheets is prepared on carbon cloth. Cyclic voltammetry, chronopotentiometry and impedance spectroscopy measurements are used to investigate electrochemical performance of as-prepared mesoporous NiCo2O4 nanosheets/carbon cloth electrode. The mesoporous NiCo2O4 nanosheets exhibit specific capacitance of 292.5 and 200 F g-1 in 2M KOH aqueous electrolyte at current densities of 1 and 8 A g-1 respectively. The cyclic performance indicates excellent capacitance retention of 94.5 % after 2000 cycles at current density of 3 A g-1. The excellent cyclic stability can be attributed to the mesoporous, high specific surface area and narrow pore distribution of nanosheets. The synthesis of mesoporous NiCo2O4 nanosheets using microwave method proves to be excellent electrode material for advanced flexible supercapacitor.