The optical second harmonic generation from a thin magnetic film on a nonmagnetic substrate is theoretically investigated for both s- and p-polarized incident light. The contributions of lattice misfit strain as well as of misfit dislocation strain to the second-order nonlinear optical susceptibility are described using a nonlinear photoelastic tensor, together with the contribution of magnetization described by a nonlinear magneto-optical tensor. (C) 2000 American Institute of Physics. [S0021-8979(00)27308-8].