Samples of nominal composition Fe0.8—xMnxAl0.2 (0 ≤ x ≤ 0.3) were prepared by mechanical alloying from high-purity powder elements. Milling times of 24, 72, 144 and 308 h and a sample-balls weight ratio of 1:12 were considered in the present study. The room temperature magnetic properties were studied by using 57Fe Mössbauer spectroscopy and vibrating sample magnetometry. Thus, the Mn content dependences of the average hyperfine field, the specific magnetization and the coercive force were obtained. Results revealed the occurrence of a ferro–paramagnetic Mn driven phase transition attributed to the increase of competitive interactions. The Mn concentration for which this transition occurs, was influenced by the milling time and the structure. The phase distribution of the samples was determined through X-ray diffraction from which structural phase changes of the type b.c.c. to f.c.c. were detected. Such changes were also strongly influenced by the milling time and the Mn concentration. Hence, the manganese and the milling time appeared as stabilizing factors of the f.c.c. phase inducing a paramagnetic behavior.