Using in situ optical microscopy, electron backscatter diffraction analysis, and atomistic simulations, we studied co-zone {1¯012} twin interaction in magnesium single crystal under compression–tension along the [101¯0] direction. Two co-zone twins are activated and interact with each other, resulting in two types of tilt boundaries that have habit planes (0001) and (101¯0) and prevent twin-across-twin transmission but facilitate the propagation of a basal slip band. Upon strain reversal, the unfavorable dissociation of dislocations in the formed tilt boundaries hinder de-twinning.