Nanostructured manganese-cobalt mixed oxide (MnCoOx) is straightforwardly prepared via one-step dealloying of the MnCoAl ternary alloy in mild alkaline solution. The as-made MnCoOx has the micro-/nano- architecture with the first order interconnected microsphere buildings and rich voids accompanied with the second order interlaced nanosheet assemblies on the microsphere. Upon leaching out the Al atoms from the MnCoAl source alloy, the residual Mn and Co atoms go though the natural oxidation at the metal/electrolyte interface to generate the MnCoOx microspheres. Electrochemical tests suggest that the as-made MnCoOx anode has the exceptional reversible capacity and rate capability at the high current rate of 1500mAg−1. Especially, the MnCoOx microspheres achieve much higher capacities and longer cycle life both at the current rates of 300 and 1000mAg−1. The MnCoOx microspheres show the prospective applications as an advanced anode in LIBs with the advantages of unusual lithium storage performance and easy preparation.