NiCuZn ferrite nanoparticles having the chemical composition Ni0.5Cu0.1Zn0.4Fe2O4 were synthesized by the microwave direct denitration (MDD) method from a mixture of metal nitrate hydrate solutions. A single-phase of NiCuZn ferrite powder with an average particle diameter of about 30 nm could be obtained using this method at reaction temperatures higher than 900 degrees C. This diameter was less than one-fifth of that obtained by the conventional solid-state reaction (SSR) method. Therefore, the NiCuZn ferrite synthesized by MDD method had a higher sinterability than the SSR method. It was categorized as a soft ferromagnetic material and its saturation magnetization was three times more than of the SSR. Its coercivity was about half of that by the SSR method. For the NiCuZn ferrite sintered with Bi2O3 additive, the saturation magnetization obtained from the MDD method was about 80% of that of the SSR method, while the coercivity was almost identical.