The asymmetric unit of the title compound, [Mn(C(6)H(6)N(4))(2)(H(2)O)(2)](C(8)H(4)O(4)), contains one-half each of the centrosymmetric cation and anion. The Mn(II) atom is coordinated by four N atoms [Mn-N = 2.2168 (14) and 2.2407 (14) Å] from two 2,2'-biimidazole ligands and two water mol-ecules [Mn-O = 2.2521 (14) Å] in a distorted octa-hedral geometry. Inter-molecular N-H⋯O and O-H⋯O hydrogen bonds consol-idate the crystal packing, which also exhibits π-π inter-actions between five-membered rings, with a centroid-centroid distance of 3.409 (2) Å.