The benzimidazolone part of the title mol-ecule, C10H8N2O, is almost planar [r.m.s. deviation = 0.014 (1) Å] and the NCH2C CH group forms a dihedral angle of 67.95 (6)° with its best plane. In the crystal, mol-ecules form inversion dimers via pairs of N-H⋯O hydrogen bonds. C-H⋯O inter-actions connect the dimers, forming a two-dimensional polymeric network parallel to (100).