LaB2C2 crystallizes in the tetragonal P4_2/mmc space group. The structure is three-dimensional. La2+ is bonded in a 8-coordinate geometry to eight equivalent C4- atoms. All La–C bond lengths are 2.86 Å. B3+ is bonded in an L-shaped geometry to two equivalent C4- atoms. Both B–C bond lengths are 1.62 Å. C4- is bonded in a 2-coordinate geometry to four equivalent La2+, two equivalent B3+, and one C4- atom. The C–C bond length is 1.43 Å.