A positive electrode material for lithium ion battery applications was successfully synthesized using microwave irradiation. This microwave synthesis has several merits such as homogeneity of final product and much shorter reaction time compared to conventional synthetic methods. We synthesized spherical [Ni0.4Co0.2Mn0.4](OH)2 as a precursor by a co-precipitation method. The pelletized mixture of the precursor and lithium hydroxide was calcined under different reaction times and temperatures by applying 1200W of microwave irradiation at 2.45GHz. We determined the optimum conditions of microwave synthesis for positive electrode materials. The powders were characterized by X-ray diffraction, scanning electron microscopy, and electrochemical testing. The capacity, its retention, and thermal stability of Li[Ni0.4Co0.2Mn0.4]O2 synthesized by the microwave synthesis were comparable to the Li[Ni0.4Co0.2Mn0.4]O2 prepared by the high temperature calcination method.