An iron(II)-catalyzed three-component reaction of O-acyl oximes, sulfur dioxide, and N-vinylacetamides is accomplished. Diverse (E)-β-sulfonyl enamines are obtained in moderate to good yields by using this protocol with excellent stereoselectivity and regioselectivity under mild conditions. Various sensitive functional groups are compatible, and a broad reaction scope is presented. A plausible mechanism is proposed, which undergoes a radical pathway through a α-carbon radical intermediate generated from iron-catalyzed ring-opening C–C bond cleavage of O-acyl oxime.