Nitroketene dithioacetals(2) were prepared in moderate to high yields by nitrodeacetylation reaction from α-acetyl ketenedithioacetals(1) when treated with mixed acid in dichloromethane at room temperature. This reaction involves an electrophilic addition-deacetylation mechanism and shows the nucleophilicity of the α-carbon atom in α-oxo ketenedithioacetals.