In the cation of the title salt, C4H10NO(+)·C24H20B(-)·C2H3N, the C-N bond lengths are 1.2864 (16), 1.4651 (17) and 1.4686 (16) Å, indicating double- and single-bond character, respectively. The C-O bond length of 1.2978 (15) Å shows double-bond character, pointing towards charge delocalization within the NCO plane of the iminium ion. C-H⋯π inter-actions are present between the methine H atom and two of the phenyl rings of the tetra-phenyl-borate ion. The latter forms an aromatic pocket in which the cation is embedded. The iminium ion is further connected through a C-H⋯N hydrogen bond to the aceto-nitrile mol-ecule. This leads to the formation of a two-dimensional supramolecular pattern along the bc plane.