Monodisperse porous Ni0.5Zn0.5Fe2O4 nanospheres have been successfully synthesized by the solvothermal method. The diameter of the nanospheres can be tuned by controlling the reactant concentration. Lower reactant concentration is favoured for the synthesis of mesoporous Ni0.5Zn0.5Fe2O4 nanospheres with higher surface area. The electrochemical results show that mesoporous Ni0.5Zn0.5Fe2O4 nanospheres exhibit high reversible specific capacity (1110 mAh g-1) for Li storage and high capacity retention, with 700 mAh g-1 retained up to 50 cycles. The excellent electrochemical properties could be attributed to the large surface area and mesoporous structure. The results suggest that Ni0.5Zn0.5Fe2O4 could be a promising high capacity anode material for lithium ion batteries.