Polycrystalline films of Sn-substituted MnSb have been prepared from bulk by Flash evaporation. The Faraday rotations and optical absorption coefficients of MnSb1−xSnx (0⩽x⩽0.3) films are measured in the visible region. Room temperature specific saturation rotation F, decreases with increasing Sn concentration at all wavelengths while the optical absorption coefficient α (uncorrected for reflection) does not show any significant change. The Magneto-optic figure of merit (2F/α) for different compositions and wavelengths are estimated for evaluating these films as beam-addressable storage elements.