FMR formulas for (001) cubic films with an applied uniaxial or isotropic in‐plane stress σ are derived for various film orientations toward the external magnetic field H. The resonance field shift δH caused by σ is explicitly evaluated including quadratic terms (∼ σ2) and the magnetocrystalline anisotropy effect. Measurements of δH performed on LPE garnet thin films (composition Y3Fe4.87Mn0.13O12) are well described by the theory.