The disordered antiferromagnetic γ-FeMn alloys in the range of Mn concentration from 0 up to 50 at.% Mn were investigated by means of X-ray diffraction analysis (XRD), differential scanning calorimeter (DSC) and Mössbauer spectroscopy (ME) at room temperature and at 80 K. The lattice parameter is constant for Mn contents below 27 at.% and increases linearly for higher Mn concentration. The RT Mössbauer spectra for the alloys with less than 20 at.% Mn were fitted with quadrupole splitting ( QS) distribution, and above 20 at.% Mn they were fitted with magnetic hyperfine field (HF) distribution. The average QS decreases, while the HF maintain a constant value by increasing the Mn concentration. At 80 K, the HF increases linearly up to 30 at.% Mn and then maintains a constant value at about 38 kOe. The peak of the specific heat ( c p) at the Néel temperature changes from broad to sharp as the Mn content increases. The Néel temperature increases with Mn concentration.