The reaction of CdCl2, 18-crown-6 and KI in water yields the title coordination polymer, [{K(C12H24O6)}2Cd2I6]n. The potassium ion lies approximately in the plane of the crown ether, coordinated by all six crown ether O atoms and also by an iodide anion bound to a cadmium atom. A C atom of the crown ether is disordered over two positions with site occupancies of 0.77 (2) and 0.23 (2). Two K(18-crown-6)+ units are linked by inversion symmetry, forming a [bis­(μ2-18-crown-6)dipottasium] system with approximately square-planar K2O2 units. Inversion symmetry also generates the Cd2I6 fragment and the polymeric system is extended along the c axis by the formation of K—I—Cd bridges.