Solid oxide fuel cells typically operate at temperatures near 800 °C. One obstacle to reducing this temperature is finding a high-performance cathode for lower temperatures. La2NiO4+δ (LNO) has shown promise as a good material as a cathode being a well-known mixed electronic and ionic conductor. However, increasing the surface exchange in LNO is important for high performance applications. Mn substitution has been shown to increase the surface exchange of LNO with Sr required to stabilize the structure. Changing the ratio of Mn:Sr will change the oxidation state of Mn and Ni and the fundamental properties of the material. Changing the Sr content in (La1-xSrx)2(Ni0.9Mn0.1)O4+δ was investigated with x = 0.1-0.5. The XRD patterns shows a single phase K2NiF4 structures. Above 35% Sr the ‘a’ parameter of the unit cell starts increasing and the ‘c’ parameter starts to decrease. Increasing Sr content showed increased electrical conductivity from 40 S cm−1 to 261 S cm−1. Impedance data of the 10% Sr sample showed behavior similar to LNO sample with slightly increased area specific resistance (ASR); any further increase in Sr content further increases ASR of the electrode.