This work adopts a thermal decomposition (TD) method for fabricating electrochemically exfoliated graphene (ECG)-modified ruthenium oxide thin film as the electrode material for high-performance supercapacitors. The TD technique consists of three consecutive thermal annealing steps for layer-by-layer coating of RuO2/ECG on the Ti substrate. We have demonstrated that the ECG content is the key factor influencing the electrochemical performance of the composite electrodes. The introduction of an appropriate amount of ECG within the composites facilitates the utilization of RuO2 and enables high capacitance, low charge transfer resistance, high rate capability, and superior durability. An optimal ECG content (5 wt.%) mixed with deposited RuO2 forms a three-dimensional conductive framework, capable of offering a synergistic effect for enhanced charge transfer as well as fast ionic diffusion. The specific capacitance of the RuO2/ECG electrode reaches as high as 407 F g−1 while maintaining the high capacitance (> 97%) during prolonged cycling (2000 cycles). The Ragone plot confirms that the RuO2/ECG capacitor enables a high energy density of 10.2 Wh kg−1 while delivering a remarkable power density of 9.2 kW kg−1. The RuO2/ECG composite developed in this work paves the way for designing robust electrode materials for high-performance supercapacitors.