The Charpy impact behavior was examined at room temperature on the basis of the metastable -type Ti-15Mo alloy with {332}<113> twinning-induced plasticity (TWIP) effect. This TWIP alloy exhibited an excellent impact toughness of approximately 250J/cm(2), which was approximately four times higher than those of common titanium alloys. The elongated dimples, fine dimples, and serpentine glide morphology were observed on the fracture surface. The large amounts of twins were formed under impact loading, which induced the adequate plastic deformation to absorb the impact energy. The formation of these dense and fine twins effectively released the stress concentration due to the dynamic microstructure refinement effect, and the abundant cracks along the twin boundaries remarkably increased the crack propagation path. The delayed crack initiation and enhanced crack propagation resistance further consumed the impact energy.