Sodium-ion batteries with good electrochemical performance are of great significance for grid-scale energy storage applications. Herein, an aqueous rechargeable Na-ion battery has been fabricated with multiwalled carbon nanotube (MWNT)-containing NaTi2(PO4)3/MWNTs nanocomposites as the anode and Na0.44MnO2 nanorods as the cathode in a 1 M aqueous Na2SO4 electrolyte and the device was carefully studied. Owing to the open framework structures (containing large interstitial sites) that both NaTi2(PO4)3 and Na0.44MnO2 possess, the fast Na-ions will facilitate free transport. Benefiting from their unique structural features, the aqueous battery system exhibited an average charge and discharge voltage of approximately 1.1 V, a high energy density of 58.7 Wh kg−1 in terms of total electroactive materials, and could deliver a reversible capacity of approximately 50 mAh g−1 after 300 cycles at 2 C rate; the corresponding coulombic efficiency was nearly constant at approximately 95 %. These results, together with the safety and cost perspectives of aqueous electrolytes indicated that the aqueous Na-ion battery may be a good candidate for safe, inexpensive, high-power energy storage systems.