Single crystals of Co(3)(PO(4))(2)·4H(2)O, tricobalt(II) bis-[ortho-phosphate(V)] tetra-hydrate, were obtained under hydro-thermal conditions. The title compound is isotypic with its zinc analogue Zn(3)(PO(4))(2)·4H(2)O (mineral name hopeite) and contains two independent Co(2+) cations. One Co(2+) cation exhibits a slightly distorted tetra-hedral coordination, while the second, located on a mirror plane, has a distorted octa-hedral coordination environment. The tetra-hedrally coordinated Co(2+) is bonded to four O atoms of four PO(4) (3-) anions, whereas the six-coordinate Co(2+) is cis-bonded to two phosphate groups and to four O atoms of four water mol-ecules (two of which are located on mirror planes), forming a framework structure. In addition, hydrogen bonds of the type O-H⋯O are present throughout the crystal structure.