The structure of the title compound, ammineaquadi-mu(5)-phosphato-trizinc(II), [Zn(3)(PO(4))(2)(H(2)O)(0.8)(NH(3))(1.2)], consists of two parts: (i) PO(4) and ZnO(4) vertex-sharing tetrahedra arranged in layers parallel to (100) and (ii) ZnO(2)(N/O)(2) tetrahedra located between the layers. Elemental analysis establishes the ammine-to-water ratio as 3:2. ZnO(2)(N/O)(2) tetrahedra are located at special position 4e (site symmetry 2) in C2/c. The two O atoms of ZnO(2)(N/O)(2) are bonded to neighbouring P atoms, forming two Zn-O-P linkages and connecting ZnO(2)(N/O)(2) tetrahedra with two adjacent bc plane layers. A noteworthy feature of the structure is the presence of NH(3) and H(2)O at the same crystallographic position and, consequently, qualitative changes in the pattern of hydrogen bonding and weaker N/O-H...O electrostatic interactions, as compared to two closely related structures.