Fracture behaviors of three directionally solidified (DS) duplex-phase alloys composed of Ni(3)Nb(D0(a))/Ni(3)Al(Ll(2)), Ni(6)TaAl(D0(24))Ni(3)Al(L1(2)) and Ni(3)Ti(D0(24))/Ni(3)Si(L1(2)) phases, respectively were investigated by three-point bending tests, focusing on temperature and orientation dependence. The temperature-toughness relation showed dissimilar curves depending on alloy. The increasing rate of fracture toughness was the highest in the Ni(3)Al/Ni(3)Nb alloy with fine lamellar structure and was the lowest in the Ni(3)Al/Ni(6)TaAl alloy with rod-like precipitates. The controlling mechanism for the temperature dependence of fracture behavior of Ni(3)Al/Ni(3)Nb alloys was discussed.