Novel porous NiO hollow microspheres are fabricated by a facile two-step method involving the ultrasound-assisted synthesis of nickel oxalate precursors and subsequent thermal annealing in air. The as-prepared NiO microspheres are composed of loosely packed nanoparticles with diameters around 30–80nm, and have a main pore distribution from 3 to 20nm with a mean pore size of 5.7nm. When evaluated as anode material for lithium ion battery, the porous NiO hollow microspheres showed enhanced electrochemical performance with high lithium storage capacity, satisfactory cyclability and rate capacity. The reversible capacity of the NiO microspheres retained 380mAhg−1 after 30 cycles at 200mAg−1. Even when cycled at various rate for more than 60 cycles, the capacity could recover to 520mAhg−1 for the current of 100mAg−1. The good lithium-storage performance can be attributed to the unique porous architecture, which provides the structural flexibility for volume change and the routes for fast Li+ diffusion.