As all-solid state batteries have garnered significant attention due to their potential to enable high-energy applications, the presence of only solid materials within the battery pack calls attention to the importance of mechanical properties during operation in an Electric Vehicle. Moreover, the mechanical integrity of the battery pack and its correlation to the electrochemical behavior observed becomes vital to determine the system’s performance and lifetime. Therefore, an understanding of the mechano-electrochemical behavior of all-solid state batteries is required to realize their potential benefits. In this work, the mechanical behavior of Li₂S-P₂S₅ was investigated in Li-Li symmetric cells. Ultrasonic testing and galvanostatic cycling measurements were used to characterize the mechanical and electrochemical response of Li₂S-P₂S₅ upon cycling. The evolution of the cell potential and AC impedance spectra was monitored and correlated to the change in mechanical properties observed during cycling. The electrolyte was considered isotropic and the change in elastic constants (Young’s Modulus and Shear Modulus) was evaluated as a function of current density, charge passed and amount of lithium passed. This approach can provide insight into the fracture, degradation and stability of solid electrolytes for use in all-solid state batteries.