A series of double-substituted Co4Sb11.3Te0.7-xSex skutterudites have been fabricated by combining the solid state reaction and the spark plasma sintering method, and the effects of Se substitution on the thermoelectric properties are characterized by measurements of the electrical conductivity, the Seebeck coefficient and the thermal conductivity in the temperature range of 300-800 K. Doping Se into the Co4Sb11.3Te0.7-xSex matrix suppresses the carrier concentration, and the electrical conductivity actually decreases with the Se content. However, moderate Se doping is effective in enhancing the thermoelectric performance of the n-type Co4Sb11.3Te0.7-xSex because of the resulted dramatically decreased thermal conductivity. Analyses indicate that the heightened point-defect scattering induced by Se doping together with the electron-phonon scattering induced by Te doping is responsible for the reduction of lattice thermal conductivity of these compounds. (C) 2012 Elsevier Ltd. All rights reserved.