Two dimensional (2D) porous nanostructures are of great interest due to their high surface area and rich edge sites, which are favorable for a wide variety of applications. In this communication, well-defined porous Co3O4 nanosheets (PCNSs) are successfully fabricated using graphene oxide as sacrificial template. The 2D structure and porous nature effectively provide more exposed active sites for electrochemical reaction and facilitate easier ion transportation across the sheets. As a result, the as-prepared PCNSs exhibit remarkable lithium storage performance, showing high reversible capacity of 1380 mAh g−1 even after 240 discharge/charge cycles at a current density of 500 mA g−1 and good rate capability (606 mAh g−1 at 10 A g−1). Moreover, it also shows a good electrocatalytic activity for the electrochemical oxygen evolution reaction with an overpotential of 368 mV for driving the current density of 10 mA cm−2 in 1 M KOH and a small Tafel slope of 59 mV dec−1.