Using a one-pot approach based on solvothermal reactions, we have successfully constructed nanoarchitectures consisting of MnOOH nanorods and reduced graphene oxide (RGO) - MnOOH@RGO without adding any surfactant. The nanocomposites show highly enhanced speciﬁc capacitance of 268F·g−1 at a current density of 0.5A·g−1, compared to pure MnOOH (108F·g−1). The asymmetric supercapacitors made with MnOOH@RGO nanoarchitectures and activated carbon (AC) exhibit excellent performances in energy storage. The devices can achieve a maximum energy density of 41.1Wh·kg−1 at power density of 400W·kg−1, and a maximum power density of 12.8kW·kg−1 at energy density of 10.7Wh·kg−1, based on the total mass of active materials. They also demonstrate excellent cycling durability retaining 98.3% of specific capacitance even after cycling for 5000 times. The highly enhanced capacity in energy storage of the nanoarchitectures could be attributed to high density of MnOOH nanorods with well controlled nanostructure loaded onto the surface of RGO in the one-pot synthesis and therefore dramatically improved conductivity of the nanoarchitectures in the presence of percolated graphene nanosheets.