The contractile forces in individual cells drive the tissue dynamics, such as morphogenesis and wound healing, and maintain tissue integrity. In these processes, α-catenin molecule plays as a tension sensor at cadherin-based adherens junctions (AJs), accelerating the positive feedback of intercellular tension. Under tension, α-catenin is activated to recruit vinculin, which recruits actin filaments to AJs. Here, we revealed how α-catenin retains its activated state while avoiding unfolding under tension. By using single-molecule force spectroscopy employing atomic force microscopy (AFM), we found that mechanically activated (under approximately 10 pN) α-catenin exhibited higher mechanical stability than a non-activated fragment. In addition, we demonstrated that mechanically activated α-catenin was further reinforced by vinculin binding. Our data suggest that the plastic characteristics of α-catenin, revealed in response to both mechanical and biochemical cues, enable the functional-structural dynamics at the cellular and tissue levels.