<p>To investigate the effects of Ca–Fe co-doping on the crystal structure, local lattice distortion, elemental valence states, and physical properties of GdMnO₃ ceramics, (Gd_1-<i>x</i>Ca_<i>x</i>)(Mn_1-<i>x</i>Fe_<i>x</i>)O₃ (<i>x</i> = 0.00–0.15) samples were prepared by a solid-state reaction method. XRD and Raman results confirm that all samples crystallize in a single-phase orthorhombic perovskite structure, and Ca–Fe co-doping induces lattice distortion. SEM results indicate that all synthesized samples possess relatively dense&#xa0;microstructures, with the average grain size varying non-monotonically with increasing doping content. XPS analysis reveals the coexistence of Mn³⁺/Mn⁴⁺ and Fe³⁺/Fe²⁺ mixed-valence states and demonstrates that co-doping modifies the oxygen vacancy concentration. Dielectric measurements show that the <i>x</i> = 0.10 sample exhibits a high dielectric constant while maintaining comparatively low dielectric loss. Magnetic measurements reveal that Ca–Fe co-doping modulates the low-temperature magnetic transitions and magnetization of GdMnO₃. The optical band gap initially increases slightly and then decreases with increasing doping content. These results demonstrate that Ca–Fe co-doping provides an effective means of tailoring the optical, dielectric, and low-temperature magnetic responses of GdMnO₃ ceramics through the combined effects of lattice distortion, mixed valence states, oxygen defects, and grain and grain-boundary characteristics.</p>