A 3D core-shell NiO nanowires@NiO nanosheets at nickel foam (NF) was synthesized by using two different synthesis processes. One was hydrothermal synthesis for core material and other was microwave-assisted hydrothermal synthesis for shell material. In 3 M KOH, a good electrochemical performance was shown by the as-prepared electrode in terms of specific capacitance (Cs) of 1782 F g� 1 at 1 A g� 1 with 70.33 retention of its initial capacitance after 7000 galvanic charge-discharge (GCD) cycles. An asymmetric supercapacitor (ASC) was prepared using NiO nanowires@NiO nanosheets@NF as positive and activated carbon coated NF (AC@NF) as a negative electrode and showed Cs of 110 F g� 1 with retention of 79.9 of its initial capacitance after 5000 GCD cycles. ASC exhibited the highest energy and power density of 39.18 Wh kg� 1 (at 906.59 W kg� 1) and 12.25 kW kg� 1 (at 12.66 Wh kg� 1). The superior electrochemical characteristics owing to excellent synergistic effects associated with core-shell structure of NiO nanowires and nanosheets showed a great potential of core-shell NiO nanowires@NiO nanosheets@NF composite for energy storage applications. © 2019 Elsevier B.V.