After screening different mixtures of transition metal oxides and copper-containing zeolites, it was found that CuNa-Mordenite (CuNaM) was the most interesting catalyst for the title reaction. The effect of copper ion content, reaction temperature, weight hourly space velocity of 1-methylnaphthalene and ammonia content in reaction mixture, addition of water and time-on-stream on ammoxidation of 1-methylnaphthalene over CuNaM were investigated. It was noticed that ammonia concentration was the key factor to control the distribution of products. Experimental data suggest that 1-naphthaldehyde is the intermediate of 1-naphtonitrile formation over CuNaM.