The crystal structure of potassium cerium(III) bis(sulfate) monohydrate, KCe(SO4)2.H2O, is built up from irregular independent SO4 tetrahedra, CeO9 polyhedra in the form of distorted tricapped trigonal prisms and K+ ions. Hydrogen bonding between the free water molecule and sulfate groups supplement the ionic bonds characteristic of the rest of the structure.