Abstract <p>The influence of Ca²⁺ ion concentration in La_{1 – <i>x</i>}Ca_<i>x</i>FeO_3 – γ (<i>x</i> = 0, 0.3, 0.5, 0.7, 1.0) orthoferrites on their crystal structure, oxygen vacancies, and Fe valence states has been studied by X-ray diffraction and Mössbauer spectroscopy at room temperature. The samples were synthesized by sol-gel method in air at 1200°C. Substitution of Ca²⁺ ions for La³⁺ ions leads to the appearance of mixed-valence states of Fe. After synthesis, the samples were annealed in vacuum at 650°C for 4 h, resulting in complete reduction of Fe⁴⁺ to Fe³⁺ ions. It should be noted that the samples with extreme <i>x</i> values (<i>x</i> = 0, 1) contain only Fe³⁺ ions. At <i>x</i> = 0 (LaFeO₃), there are no oxygen vacancies in the sample, while at <i>x</i> = 1 (CaFeO_2.5), their number is maximum. With an increase in the Ca²⁺ content, the number of oxygen vacancies and the Fe³⁺/Fe⁴⁺ valence ratio change. At <i>x</i> &gt; 0.5, vacancy-ordered Grenier (LaCa₂Fe₃O₈) and brownmillerite (Ca₂Fe₂O₅) phases are formed. The obtained results demonstrate the effectiveness of Mössbauer spectroscopy for studying the structural features, local iron states, and the distribution of oxygen vacancies in Ca-substituted orthoferrites.</p>