Materials with sheet-like morphologies are highly desirable candidates for energy storage and conversion applications, due to the confined atomic thickness and high surface area, which would largely improve the electrochemical reaction kinetics. In this work, the sodium storage performance of TiSe 2 nanosheets and corresponding sodiation/desodiation reaction mechanism are studied for the first time. TiSe 2 nanosheets are readily exfoliated from bulk TiSe 2 after quick ultrasonication or grinding. The TiSe 2 nanosheets exhibit a reversible capacity of 147mAhg -1 at 0.1Ag -1 , and show excellent rate capability with a capacity of 103mAhg -1 at an ultra-high current density of 10.0Ag -1 . The combined in situ XRD and ex-situ HRTEM results suggest that sodium storage in TiSe 2 is achieved through a multi-step intercalation/deintercalation mechanism. Besides, TiSe 2 might be a promising 2D nanomaterial platform for other energy and electronic applications due to its easy exfoliation and unique physicochemical properties.