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Maghemite-silica nanocomposites consisting of 5nm magnetic nanoparticles dispersed in silica xerogel were prepared by the sol–gel technique. The thermal stability of samples with 0.013 and 0.200Fe/Si molar ratio was investigated in the temperature range of 120–1400°C by X-ray, FTIR and Micro-Raman spectroscopy. Depending on the nanoparticle content, the silica matrix provides extra stabilization of γ-Fe₂O₃ nanoparticles against transformation into α-Fe₂O₃ and ɛ-Fe₂O₃. In nanocomposite samples presenting low nanoparticle concentration, γ-Fe₂O₃ was the only iron oxide phase found up to 900°C. However, above 900°C, ɛ-Fe₂O₃ was the dominant phase. For high nanoparticle contents, mixtures of α-Fe₂O₃ and γ-Fe₂O₃ phases were identified at 500 and 700°C, though α-Fe₂O₃ and ɛ-Fe₂O₃ phases were found at higher temperatures.