Extended X-ray absorption fine structure and X-ray absorption near edge structure techniques were used to study in detail the formation of FeCo alloy nanoparticles in a silica matrix during their sol-gel preparation. Depending on the Fe and Co precursors, different intermediate products are formed, ferrihydrite and Co3O4 starting from nitrate precursors and cobalt ferrite starting from acetate precursors. The final nanocomposites contain bcc FeCo nanoparticles which are sometimes accompanied by fcc Co depending both on the intermediate products and on the porous structure of the samples.