Indium oxide-doped hematite xIn 2 O 3 * (1 − x)α-Fe 2 O 3 (molar concentration x = 0.1-0.7) solid solutions were synthesized using mechanochemical activation by ball milling. XRD patterns yield the dependence of lattice parameters and grain size as function of milling time. After 12 h of milling, the completion of In 3+ substitution of Fe 3+ in hematite lattice occurs for x = 0.1. For x = 0.3, 0.5 and 0.7, the substitutions between In 3+ and Fe 3+ into hematite and respectively, In 2 O 3 lattices occur simultaneously. The lattice parameters of α-Fe 2 O 3 (a and c) and In 2 O 3 (a) vary with milling time. For x = 0.1, Mössbauer spectra were fitted with one, two, or three sextets versus milling time, corresponding to gradual substitution of In 3+ for Fe 3+ in hematite lattice. For x = 0.3, Mössbauer spectra after milling were fitted with three sextets and two quadrupole-split doublets, representing In 3+ substitution of Fe 3+ in hematite lattice and Fe 3+ substitution of In 3+ in two different sites of In 2 O 3 lattice. For x = 0.5 and 0.7, Mössbauer spectra fitting required two sextets and one quadrupole-split doublet, representing coexistence of In 3+ substitution of Fe 3+ in hematite lattice and Fe 3+ substitution of In 3+ in indium oxide lattice. The recoilless fraction studied versus milling time for each molar concentration exhibited low values, consistent with the occurrence of nanoparticles in the system. SEM/EDS measurements revealed that the mechanochemical activation by ball milling produced xIn 2 O 3 * (1 − x)α-Fe 2 O 3 solid solution system with a wide range of particle size distribution, from nanometer to micrometer, but with a uniform distribution of Fe, In, and O elements.