The title compound C21H21O3PSe, is comprised of a P atom in a distorted tetrahedral environment, attached to the selenium atom and three carbons from the phenyl rings. The phosphorus–selenium bond length is 2.1194 (11) Å. All three methoxy groups are nearly co-planar with their respective phenyl rings, with the angles between the phenyl ring and the C—O bond of the methoxy groups being 6.2 (2), 3.1 (2), and 5.7 (2)°. The torsion angles of the phenyl rings relative to the P=Se bond are 55.84 (19), 176.18 (16), and 63.9 (2)°. No strong interactions were observed, but in addition to van der Waals forces, there are close contacts between C—H...π and C—H...Se.
