Coupling of propagating magnetostatic waves with resonant exchange dominated spin wave modes produces attenuation notches in the magnetostatic wave transmission response. The exchange resonances occur when kex=n&pgr;/d, where kexis the exchange wave number normal to the film plane, n is the mode number and d is the thickness of the epitaxial YIG film. Measurements of attenuation notch depth and position have been performed on as grown LPE‐YIG films and on films whose surface spins were pinned by ion milling, SiO2deposition or annealing. Coupling was strongest for magnetostatic volume waves with the magnetic bias field normal to the film. Coupling to magnetostatic surface waves was less strong and in accordance with theory magnetostatic volume waves propagating parallel to the magnetic bias field showed zero coupling. The various treatments increased the depth of the attenuation notches and produced a mode pattern consistent with spin pinning asymmetric between the two film surfaces. The probable source of coupling between the propagating magnetostatic waves and resonant exchange modes in as grown films are magnetic non‐uniformities in the YIG films due to transient layer or melt depletion effects.