The magnetic properties of the FexMn0.7−xAl0.30 (0.40⩽x⩽0.58) alloy series have been investigated by means of Fe57 Mössbauer spectroscopy and ac magnetic susceptibility measurements. From our data, we propose a magnetic phase diagram for the system which is adequately reproduced by a diluted and random-bond Ising model which was analyzed on the basis of the mean-field renormalization-group method.