Structural and magnetic properties of rare-earth doped (Sr 2 − x Gd x )FeMoO 6 compounds (x=0, 0.05, 0.1, 0.13 and 0.15) have been investigated. All the compounds are of single phase and belong to the space group I4/m. Because of the small size of Gd 3+ ion (compared to that of Sr 2+ ion), obvious structural distortion is introduced in the compounds and imposes an important influence on the magnetic property of (Sr 2 − x Gd x )FeMoO 6 . The competing interaction between structural distortion and electron injection results in a non-monotonic evolution of the Curie temperature (T C ): T C decreases firstly and then increases, with a minimum value at x≈0.07. Contrary to the magnetic behavior of Eu 3+ ion in (SrEu)FeMoO 6 compound, the long-range ordered Gd 3+ moment is parallel to that of Fe 3+ ion at low temperature, and the contribution of the dopant to the saturation magnetization of (Sr 2 − x Gd x )FeMoO 6 is 6.75–7.15μ B per Gd 3+ ion, which is comparable to the magnetic moment of a free Gd 3+ ion (7.0μ B ). Above results indicate that although the rare earth elements exhibit similar chemical and optical character, their magnetic behavior in Sr 2 FeMoO 6 compound differs to a large degree.