Understanding the effects of lattice strain on oxygen surface and diffusion kinetics in oxides is a controversial subject that is critical for developing efficient energy storage and conversion materials. In this work, high-quality epitaxial thin films of the model perovskite La0.5Sr0.5Mn0.5Co0.5O3-δ (LSMC), under compressive or tensile strain, were characterized with a combination of in situ and ex situ bulk and surface-sensitive techniques. The results demonstrate a non-linear correlation of mechanical and chemical properties as a function of the operation conditions. It was observed that the effect of strain on reducibility is dependent on the “effective strain” induced on the chemical bonds. In plain strain, and in particular the relative B-O length bond, are the key factor controlling which of the B-site cation would be reduced preferentially. Furthermore, the need to use a set of complimentary techniques to isolate different chemically-induced strain effects was proven. With this, it was confirmed that tensile strain favors the stabilization of a more reduced lattice, accompanied by greater segregation of strontium secondary phases and a decrease of oxygen exchange kinetics on LSMC thin films.