Results of investigations on the microstructural features of β(B2) + γ'(L1 2 ) two-phase Ni-Al-Fe alloys fabricated through various thermomechanical processes are reported. It is found that three types of β + γ' structures: blocky, lamellar and widmanstatten structures, are formed when alloys quenched from high temperatures are reannealed at 800 o C. The formation of the blocky structure is brought about by the following successive reactions, the β -> β'(L1 0 ) martensitic transformation, the β' -> Ni 5 Al 3 (Pt 5 Ga 3 type) ordering reaction and the Ni 5 Al 3 -> β + γ' transition similar to a discontinuous transition occurring during heating up to 800 o C. On the other hand, the lamellar structure results from the Ni 5 Al 3 -> γ' transition and a heterogeneous precipitation of the β phase on the boundaries between the γ' variants after the formation of the Ni 5 Al 3 from the β' phase. It is also observed that the mechanical properties are affected by the type of microstructures present. These results suggest that the Ni-Al-Fe dual-phase alloys are amenable to microstructural control through thermomechanical treatments to realise optimum mechanical properties as in the case of Fe base alloys.