In the title polymeric coordination compound, [Sn(CH(3))(3)(C(6)H(5)O(2)Se)](n), the Sn(IV) atom has a distorted trigonal-bipyramidal geometry, with two O atoms of two symmetry-related bridging phenyl-seleninate anions in axial positions and three methyl groups in equatorial positions. In the crystal, the complex exhibits a chain structure parallel to the b axis.