Two series of skutterudite materials, Co4Sb11.3Te0.7-x S (x) (x = 0.07-0.2) and Co4Sb12-x S (x) (x = 0.07-0.15), were synthesized through solid state reaction and consolidated by spark plasma sintering. The samples were characterized by powder X-ray diffraction, electron probe analysis, and measurements of electrical conductivity, Hall coefficient, Seebeck coefficient, and thermal conductivity. The results indicate that sulfur in Co4Sb12-x S (x) most likely forms the CoSbS compound and is unlikely to get into the CoSb3 lattice, while it can dissolve in Co4Sb12-x Te (x) compounds due to the radius compensation when fabricated by the methods in this study. The lattice thermal conductivity decreases from 2.07 Wm(-1) K-1 for tellurium single-doped Co4Sb11.3Te0.7 to 1.46-1.67 Wm(-1) K-1 for Co4Sb11.3Te0.7-x S (x) (x = 0.07-0.20) at 800 K. The thermoelectric performance is significantly enhanced by tellurium-sulfur co-doping in Co4Sb11.3Te0.7-x S (x) compounds, and a peak dimensionless figure of merit similar to 1.1 is achieved in Co4Sb11.3Te0.63S0.07. The enhancement is mainly attributed to the great reduction of the lattice thermal conductivity due to the increased phonon scattering by the sulfur defect.