The structural evolution of a binary alloy with nominal composition Fe25Se75 prepared by ball milling was investigated as a function of milling time. The X-ray diffraction (XRD) patterns showed that for milling times up to 20 h, the FeSe2 phase is formed and excess selenium remains in the amorphous state. For milling times between 40 and 52 h, FeSe2 is partially transformed to β-FeSe and/or Fe7Se8. The structural evolution of the mixture with milling time was followed using the XRD, differential scanning calorimetry and Raman spectroscopy techniques.