The two new title complexes, [Mn(C5H3N6)2(H2O)2] and [Zn(C5H3N6)2(H2O)2], are isomorphous. In both compounds, the metal atom is located on an inversion center and is coordinated by four N atoms from two 5-(pyrazin-2-yl)-1H-tetrazolate anions in the basal plane and by two O atoms of water ligands in the apical positions to form a distorted octahedral geometry. Intermolecular hydrogen-bond interactions between the uncoordinated N atoms of the tetrazolate anions and the H atoms of the water molecules lead to the formation of a three-dimensional network.