In this paper, an isolated multi-resonant three-port bidirectional direct current-direct current (DC-DC) converter is proposed, which is composed of three full bridges, two inductor-capacitor-inductor-capacitor (LCLC) multi-resonant tanks and a three-winding transformer. The phase shift control method is employed to manage the power transmission among three ports. Relying on the appropriate parameter selection, both of the fundamental and the third order power can be delivered through the multi-element LCLC resonant tanks, and consequently, it contributes to restrained circulating energy and the desirable promoted efficiency. Besides, by adjusting the driving frequency under different load conditions, zero-voltage-switching (ZVS) characteristics of all the switches of three ports are guaranteed. Therefore, lower switching loss and higher efficiency are achieved in full load range. In order to verify the feasibility of the proposed topology, a 1.5 kW prototype is established, of which the maximum efficiencies under forward and reverse operating conditions are 96.7% and 96.9% respectively. In addition, both of the bidirectional efficiencies maintain higher than 95.5% when the power level is above 0.5 kW.