Phase equilibria were established in the Ce–Co–Sb ternary system at 400°C based on X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS) techniques. Fourteen binary compounds Ce 24 Co 11 , CeCo 2 , CeCo 3 , Ce 2 Co 7 , Ce 5 Co 19 , Ce 2 Co 17 , CoSb, CoSb 2 , CoSb 3 , Ce 2 Sb, Ce 5 Sb 3 , Ce 4 Sb 3 , CeSb and CeSb 2 have been confirmed, and three ternary compounds CeCoSb 3 , CeCo 1−x Sb 2 and CeCo 1.33 Sb 2 are found in this system at 400°C. The isothermal section of this system at 400°C consists of 20 single-phase regions, 40 two-phase regions and 21 three-phase regions. The compound CeCo 1−x Sb 2 has ZrCuSi 2 -type structure with space group P4/nmm, a=0.3878nm and c=0.9849nm. The crystal structure for the compound CeCoSb 3 is determined to be CeNiSb 3 -type (Pbcm) with a=1.27697nm, b=0.60601nm and c=1.8435nm. The compound CeCo 1.33 Sb 2 is of orthorhombic system with a=0.6083nm, b=0.60118nm and c=1.04596nm. The homogeneity range of CoSb phase is about 2at.%. The solubilities for the other single-phase regions were not observed.