The present work investigated the microstructural evolution and mechanical properties of ternary Ni-25Al-xFe alloys, which are the NiAl system macroalloyed with iron. The aim is to get an understanding of the relationship between the microstructures and the mechanical properties. The results reveal that the suitable additions of Fe can change the NiAl from a single beta'-phase granular structure to a multi-phase dendritic one. The alloys with such a microstructure could possess better mechanical properties because of the main plastic deformation was supported by the softer gamma phase in the interdendritic regions. In this Ni-25Al-xFe alloy system, the chemical compositions of the alloys influenced the morphologies of the interdendrites, and therefore strongly affected on the hardness and tensile properties. Thus, to control the microstructure, it is very important to get a Ni-Al-Fe intermetallic alloy with a better combination of mechanical properties. In addition, the variation of the room-temperature tensile properties could be explained by the concept of plastic zone size influenced on the state of stress.