FeCo-Al2O3 nanocomposite aerogels were studied by high-resolution electron microscopy, energy filtered transmission electron microscopy, Mössbauer spectroscopy, and measurements of static magnetizations and hysteretic behavior. The combined use of such techniques provided insights on the formation of bcc FeCo nanocrystalline particles inside the alumina matrix, which is promoted by thermal treatment under hydrogen flow of the parent aerogel. Sample characteristics such as alloy composition and crystallinity, influence of the matrix on the structural evolution, and resulting magnetic properties were investigated as a function of the temperature and time of the reduction treatment.