Pressed strontium ferromolybdate (Sr2FeMoO6−δ) pellets with different oxygen indices δ and degrees of superstructural ordering (SO) are synthesized by solid‐phase and citrate‐gel methods to study magnetic and electric transport behaviors of this compound. The crystalline structure of the samples is found to demonstrate ordering of the Fe and Mo cations, which increases with increase in δ. The saturation magnetization and the Curie temperature of the samples correlate with the degree of SO. The Banerjee criterion indicates that the compounds studied undergo a second‐order phase transition. The temperature dependence of the isothermal change of entropy in magnetic field is determined by the Maxwell approach. The additional low‐temperature annealing is found to change the sample conductivity of metallic type for semiconducting one and significantly increases the magnetoresistance due to intergrain electron tunneling.