The Fe2VAl Heusler alloy was reported to have good thermoelectric properties. Because the natural resource of vanadium is insufficient, Fe2TiAl based alloys were studied. Ni, Co, or Cr was substituted to stabilize the Heusler structure and to control the valence electrons. The Seebeck coefficients decreased in the Heusler single-phase region when these fourth elements were added, probably because the Fermi level was lying above the minimum in the density of state. The maximum and minimum Seebeck coefficients were +50 microV/K in Fe2(Ti0.6Cr0.4)Al and ¡-34 microV/K in (Fe0.2Co0.8)2TiAl, respectively. Their electric conductivities were metallic judged by their temperature dependency. The characteristic semiconducting behavior of the Fe2VAl Heusler alloy due to a pseudo gap in the density of state was not observed in the substituted Fe2TiAl alloys.