The ammoxidation reaction of toluene over CuNa-ZSM-5 catalysts has been investigated. CuNa-ZSM-5 showed the best activity and selectivity for benzonitrile formation among [Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Ag(I)] ion-exchanged CuNa-ZSM-5. It was found that Cu(II) in the zeolite matrix readily forms an ammine complex with ammonia and a charge transfer complex with toluene and, when ammonia and toluene were added concurrently, [Cu(II) (ammonia) (toluene)] complex was formed and remained at the typical reaction condition. Changes in the reaction pattern for the ammoxidation of toluene under the various reaction conditions can be explained in terms of the stability of the [Cu(II) (ammonia) (toluene)] complex. We tentatively formulated the mechanistic scheme for the ammoxidation reaction of toluene over the CuNa-ZSM-5 catalyst. The present work shows that the [Cu(II) (ammonia) (toluene)] complex formed in the CuNa-ZSM-5 seemed to offer a new reaction pathway which was different from those over the metal oxide catalysts.