The cyclo-tetra-phosphate anion, [P(4)O(12)](4-), forms the title complex with cobalt(II) and quinolinium, {(C(9)H(8)N)(2)[Co(P(4)O(12))(H(2)O)(2)]·6H(2)O}(n). In the complex anion, the Co(II) ion, lying on an inversion center, is surrounded by four phosphate O atoms and two water mol-ecules in a slightly distorted octa-hedral geometry. The crystal structure consists of anionic ribbons of formula {[Co(P(4)O(12))(H(2)O)(2)](2-)}(n) extending along [100]. A network of O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds consolidates the crystal packing.