Poly[3-(methacrylamido) propyltrimethylammonium chloride] (PMAPTAC) with a well-controlled structure was reacted with FeCl3 to exchange the counter anion from chloride (Cl-) to tetrachloroferrate (FeCl4-) to prepare a magnetic-responsive polymer (PMAPTAFe). PMAPTAFe powder was attracted to a neodymium magnet. A cast film of PMAPTAFe, which can be prepared from the aqueous solution, also showed magneticresponsive behavior.