<p>Gd_1−<i>x</i>Sr_<i>x</i>MnO₃ samples are synthesized via the solid-state synthesis route. The role of Sr²⁺ substitution at Gd positions on the structural and magnetic properties of Gd_1−<i>x</i>Sr_<i>x</i>MnO₃ is studied. The results indicate that Sr substitution leads to lattice expansion but does not alter the orthorhombic structure of the gadolinium manganate (GdMnO₃) system. EDS analysis further confirms the element composition with presence of Sr element in the Sr substituted GdMnO₃. The change of Raman peaks suggests that the Sr ions have effectively substituted Mn ions and induces lattice disorder. The replacement of Sr²⁺ with a lower valence state for Gd³⁺ increases the valence state of Mn³⁺ and creates oxygen vacancies, and the charge compensation in Sr-substituted GdMnO₃ is mainly achieved by the formation of Mn^4+. Sr substitution can adjust the vacancy size and concentration in the Gd_1−<i>x</i>Sr_<i>x</i>MnO₃ samples. The magnetization values and magnetic transition temperatures of Gd_1−<i>x</i>Sr_<i>x</i>MnO₃ samples are considerably increased by Sr substitution. This study demonstrates that the neighboring Mn³⁺ and Mn⁴⁺ cations with ferromagnetic configuration induced by Sr substitution are closely related to the magnetic behaviors of Gd_1−<i>x</i>Sr_<i>x</i>MnO₃ materials at temperatures of 30 and 40&#xa0;K, and cation vacancies have strong correlation with the magnetization of Gd_1−<i>x</i>Sr_<i>x</i>MnO₃ below the critical temperature for Gd³⁺ moment alignment.</p>