Formation of dense La(Sr)Fe(Ga)O3–δ (LSFG) interlayers on the surface of La0.88Sr0.12Ga0.82Mg0.18O3–δ (LSGM) solid electrolyte by magnetron sputtering has been investigated. Their effect on electrode characteristics of the porous La0.7Sr0.3Fe0.95Ga0.05O3–δ cathodes has been studied. It is shown that the elemental composition of the interlayers depends mainly on the elemental composition of the target, whereas the conditions of deposition (discharge power, atmosphere, etc.) have an insignificant effect. The synthesized interlayers contain the larger amounts of La and Ga and the smaller amount of Sr and Fe as compared with the target composition. The introduction of the dense interlayer between the porous electrode and the electrolyte improves the electrode characteristics by making easier the transition of O2– ions across the electrode/electrolyte interface. The dense LSFG interlayers with the thickness of 600 and 800 nm decrease the polarization resistance of the electrode at 850°С by 33 and 43%, respectively.