Amorphous rare‐earth transition metal alloys of composition (Gd1−xFex)1−yAuywithx=0.74, 0.77, and 0≤y≤0.40 were prepared by evaporation onto rotating glass substrates. The magnetic and magneto‐optic properties have been investigated in the temperature range 4.2≤T≤TCrevealing a decrease of the compensation and Curie temperature, the uniaxial anisotropy, and the Faraday and Kerr rotation with increasing gold content. The temperature behavior can be interpreted in terms of a mean‐field analysis indicating a pronounced influence of the gold on the iron moment and the exchange constants. The temperature dependence of the Faraday rotation can be described in terms of the sublattice magnetizations inferred from the fit of the mean‐field theory to the measured saturation magnetization.