Abstract: The magnetic structure and the composition of Fe₃O₄/γ-Fe₂O₃ nanoparticles are studied at 300 and 80 K with Mössbauer spectroscopy. We found that the Fe₃O₄/γ-Fe₂O₃ particles are a core–shell nanocomposite (NC), in which magnetite Fe₃O₄ is covered with a maghemite shell (γ-Fe₂O₃). We showed that the thickness of the maghemite shell (γ-Fe₂O₃) depends on synthesis technology. We found that a layer, whose magnetic structure differs from that of the inner part of the shell (γ-Fe₂O₃), is formed on the surface of the maghemite shell (γ-Fe₂O₃) in the Fe₃O₄/γ-Fe₂O₃ NC. An intermediate layer is formed in the spin-glass state between the core and the shell. The data on structure of core–shell nanocomposites open up prospects to explain the properties of such particles, which are of great interest to use in various fields, including biomedicine.