In the current research, Nd2(Fe,Co)14B hard magnetic nanoparticles were synthesized through the reduction diffusion process. For this purpose, Nd(Fe1-xCox)B oxide powders for x = 0.05, x = 0.3, and x = 0.5 were heat-treated once in hydrogen atmosphere (H2) and once in the reduction diffusion process using calcium hydride (CaH2). The phase analysis and chemical composition of the resulting Nd-Fe-Co-B powders were identified by X-ray diffraction and X-ray energy dispersive spectroscopy. The morphology and magnetic properties of the synthesized powders were investigated using a field emission scanning electron microscope, transmission electron microscope, and vibrating sample magnetometer. The results demonstrated that oxide powders reduced with hydrogen gas were characterized by a soft magnetic character due to the formation of the bcc-FeCo magnetic phase. However, oxide powders reduced via reduction diffusion exhibited hard magnetic characteristics due to the direct diffusion of NdH2, Fe, Co, and B phases as well as the production of Nd2(Fe,Co)14B hard magnetic phase. The Nd2(Fe,Co)14B particles were rinsed with water and dilute acetic acid to eliminate the byproducts (CaO) formed during the reduction diffusion process. Followed by washing, coercivity dropped due to the formation of the Nd2Fe14BHx soft magnetic phase; however, saturation magnetization rose due to the elimination of the non-magnetic CaO phase from the final production.