Here we demonstrate for the first time that CFx cathodes show rechargeable capability in sodium ion batteries with an initial discharge capacity of 1061 mAh g(-1) and a reversible discharge capacity of 786 mAh g(-1). The highly reversible electrochemical reactivity of CFx with Na at room temperature indicates that the decomposition of NaF could be driven by carbon formed during the first discharge. The high reversible capacity made it become a promising cathode material for future rechargeable sodium batteries.