Graphene nanosheets are facilely prepared by electrochemical exfoliation of graphite in sodium tungstate aqueous solution. Through a filtration-transfer procedure and followed by heat treatment, the graphene nanosheets are deposited on the polyethylene terephthalate substrate to form electrothermal films. The graphene electrothermal films exhibit low square resistance of 159 Omega/sq, high in-plane thermal conductivity of 658 W/m/K, and excellent heat propagation with uniform temperature distribution. The steady-state temperature of the films increases from 32 to 139 A degrees C as the applied voltage increases from 5 to 30 V. The electrothermal response of the graphene films is as fast as < 20 s. The graphene film heaters also display good flexibility. Even after bending 100 times, the graphene film heaters still exhibit almost the same electrothermal performance.