Asymmetric transmission (AT) for circularly polarized (CP) electromagnetic (e-m) waves in chiral metamaterial (CMM) is a well-known phenomenon. However, most of the CMMs exhibit AT along only one direction. In this work, AT for CP waves with a magnitude of more than 0.5 along three principal directions of a newly made three-dimensional (3D) spline assembly is reported at terahertz frequencies. Surface current analysis is presented to explain the mechanism of AT for CP waves in the proposed 3D assembly. © 2020 Optical Society of America.