Single-phase Ti1-x(Hf0.919Zr0.081)xN iSn (x＝0.00—0.15) compounds were synthesized by solid-state reaction and high- density polycrystalline bulk material was prepared by spark plasma sintering (SP S). The effect of Hf and Zr substitution for Ti on the thermoelectric propertie s of TiNiSn half-Heusler compounds were investigated. It was shown that the subs titution of a small amount Hf and trace Zr for Ti resulted in significant reduct ion of the thermal conductivity and remarkable enhancement of the Seebeck coeff icient. As a result, the dimensionless figure of merit ZT of Ti0.85(H f0.919Zr0.081)0.15NiSn reached a high maximum v alue of 0.56 at 700K and the enhancement of ZT was 190%—310% at the same temper ature compared with ternary TiNiSn compounds.