The mechanical properties of electrode materials and solid-state electrolytes in solid-state batteries (SSBs) have an important influence on the mechanical stabilties of SSBs. Mechanical failures in SSBs on different scales and in different components will occur once the stress inside SSBs exceeds the materials’ strengths, which seriously deteriorates the electrochemical performances of SSBs. From the perspective of stabilizing the mechanical stabilities of SSBs, in this review we describe the influences of the mechanical properties of each component in SSBs on the mechanical stabilites of SSBs, and we analyze the factors that affect the mechanical properties of materials. In addition, we also discuss the mechanical failures of SSBs during cycle, including electrode materials’ or solid-state electrolytes’ fractures, electrode-electrolyte contact losses, and short-circuits due to lithium dendrites. Finally, we summarize some common strategies to mitigate the mechanical failures in SSBs, and look forward to the future research directions in this field. Overall, the mechanical failures in SSBs and their strategies discussed in this review will help researchers build SSBs with higher energy density, longer life and higher safety.