The title ionic compound, C16H36N(+)·C10H20B10N3O3(-), consists of a tetra-butyl-ammonium cation and a closo-deca-borate cluster anion, which is bound to the substituted 2,3-dihydro-1,2,4-oxadiazole ring through a B-N bond [1.540 (2) Å]. The distances between connected B atoms in the deca-borate cluster range from 1.689 (2) to 1.844 (2) Å. The 2,3-dihydro-1,2,4-oxadiazole ring adopts an envelope conformation with the N atom as the flap atom.