The title compound, C28H33N2S2P, adopts the thione tautomeric form, as supported by the C-S distance [1.6744 (18) Å]. The Schiff base exhibits an E conformation about the C=N bond but a Z conformation about the C-N bond. The terminal chain is disordered over two sets of sites with an occupancy ratio of 0.732 (3):0.268 (3). In the crystal, pairs of N-N-H hydrogen bonds between the thione groups link neighbouring mol-ecules into centrosymmetric dimers.