The title compound, C21H21O3PSe, is comprised of a P atom in a distorted tetrahedral environment, attached to the Se atom and three C atoms of the phenyl rings. The P—Se bond length is 2.1214 (12) Å. All three methoxy groups are near coplanar with their respective phenyl rings, with the angles between the phenyl ring and the C—O bond of the methoxy groups being 5.7 (2), 1.5 (4), and 5.7 (3)°. The torsion angles of the phenyl rings relative to the P=Se bond are 35.62 (10), 35.07 (13), and 44.50 (11)°. No strong intermolecular interactions were observed, but that in addition to van der Waals forces, there are C—H...π and C—H...Se close contacts.
