Dual two-phase intermetallic alloys composed of geometrically close-packed (GCP) structures of Ni3Al (L1(2)) and Ni3V (D0(22)) containing Nb were investigated in terms of microstructural evolution during low-temperature annealing (aging) and the related mechanical properties. The eutectoid region, i.e. the prior Al phase (Ni solid solution) is composed of the lamellar-like structure consisting of Ni3Al (L1(2)) and Ni3V (D0(22)) even at an early aging stage, and then coarsen with increasing aging time. The lamellar-like structure tend to align along [001] direction and on {001} plane in the prior A1 phase (or the L1(2) phase). In a wide range of temperature, the dual two-phase intermetallic alloys showed high yield and tensile strength, and also reasonable tensile ductility, accompanied with ductile fracture mode. The observed mechanical properties were less sensitive to the microstructural evolution during low-temperature annealing (aging), meaning that the present dual two-phase intermetallic alloy is promising for a new type of high-temperature structural material.