Digital shearography (DS) is a noncontact, whole-field, and laser-based optical interferometric method. It is a valuable tool in the field of nondestructive testing (NDT) and received considerable acceptance in the automotive and aerospace industries. Conventional DS only detects the flaws in one or two shearing/sensitive directions, which leads to the missed inspection and leaves quite a lot of suspected defects underdefined. A trishearing DS for NDT is proposed to solve the mentioned issue. The presented shearography is designed based on a multiplexed Mach–Zehnder interferometer embedded with the spatial phase shift technique. It measures the defects in three sensitive directions simultaneously and has balanced optical paths with high light efficiency. Moreover, the measurement sensitivity of each direction can be adjusted during the test, without affecting the carrier frequencies, so it meets various needs for NDT applications. The principle and the experimental validation of the proposed system are introduced in detail.