In the title compound, C(25)H(28)NO(2)PS, the cyclo-decene ring exhibits a crown conformation. The two dimethyl-benzene rings which are fused symmetrically on either side of the ten-membered ring, make dihedral angles of 20.2 (1) and 18.0 (1)°. The phenyl ring substituted at P is perpendicular to the heterocyclic ring, making a dihedral angle of 88.4 (1)°. The crystal structure is stabilized by very weak intra-molecular C-H⋯O hydrogen bonding.