Angular dependence of ferromagnetic resonance fields in amorphous Fe90−xCoxZr10alloys with 0≤x≤10 has been measured for both in‐plane and out‐of‐plane sample geometries. This angular variation has been fitted to theoretical resonance expressions which take into account the uniaxial anisotropy. The uniaxial anisotropy field,Hk=2Ku/Ms, increases with Co concentration and scales with saturation magnetization,Ms.