Summary To meet the increasing demand for highly efficient heat dissipation in power electronics, a heat spreader that has significantly greater isotropic thermal conductivity than the commonly used copper (400 W/m·K) should be developed. Although graphite is a promising candidate because of its high basal-plane thermal conductivity, its application is restricted by its low c axis thermal conductivity. This issue can be resolved by transforming graphite into an isotropic thermal conductor by building a structure that can effectively route heat in all three dimensions. Herein, we develop a double-decker structure with differently oriented graphite layers to realize high heat dissipation from a local heat source. The critical issue of bonding the graphite layers is overcome by a high-temperature process using Cu as the binding layer. The graphite/Cu composite efficiently dissipates heat nearly isotropically and performs as well as an isotropic conductor with a thermal conductivity of 900 W/m·K.