This paper presents an electromagnetic analysis of magnetic surface wave propagation on a thick transversely magnetized YIG slab. The effect of transverse variation of wave field has been taken in account; this leads to hybridization of TE and TM modes. Using the interface model the general dispersion relation has been obtained which reduces to the well‐known limiting forms. The numerical results indicate restricted validity of the earlier analyses. Specifically, for any realistic set of parameters, the propagation of surface wave inXband can be satisfactorily described only by the present analysis.