In the title spiro compound, C(25)H(22)N(4)S, the planar quinoxaline (r.m.s. deviation = 0.070 Å) and planar thia-diazole (r.m.s. deviation = 0.060 Å) ring systems share a common C atom; their mean planes are aligned at 89.7 (1)°. The thia-zole ring possesses two aromatic ring substituents and is nearly coplanar with these rings [the dihedral angles between the thia-diazole and phenyl rings are 5.7 (1) and 10.7 (1)°]. The allyl unit is disordered over two positions in a 0.65 (1):0.35 (1) ratio.