Nanoparticles of Nd(Fe1-xCox)B with Co concentrations ranging from x = 0 to 0.5 were prepared using a modified Pechini-type sol-gel method. We have shown the influence of Co on the morphology and size of nanoparticles, as well as on elements distribution in nanostructures. It was found that nanoparticles with increased content of Fe and Co were formed during the synthesis process. There was an interdiffusion of Nd and Fe, both after oxidation and after reduction. This study helped to define promising “bottom-up” approaches for the fabrication of nanomaterials for the advanced Nd(Fe1-xCox)B permanent magnets by chemical synthesis.