We report on the synthesis, crystal structure, physical properties, and first-principles calculations of a new borocarbide ThNiBC. The new compound was synthesized by an arc-melting method, crystallizing in a tetragonal LuNiBC-type structure with an exceptionally low axial ratio of c/a = 1.98. The physical property measurements indicate that it is a Pauli-paramagnetic metal with significant electron-electron scattering. Bulk superconductivity at T c = 0.7 K is demonstrated with zero electrical resistivity, Meissner effect, and specific-heat jump. The first-principles calculations reveal a relatively low density of states at the Fermi level with multiple electron-type Fermi surfaces.