The asymmetric unit of the title compound, C(12)H(8)N(2)·C(10)H(10)N(2)·2H(2)O, contains one half-mol-ecule of phenazine, one half-mol-ecule of naphthalene-1,5-diamine and one water mol-ecule. The phenazine and naphthalene-1,5-diamine mol-ecules are located on inversion centers. The water mol-ecules serve as bridges between the naphthalene-1,5-diamine mol-ecules and also between the naphthalene-1,5-diamine and phenazine mol-ecules. The naphthalene-1,5-diamine and water mol-ecules are connected via N-H⋯O and O-H⋯N hydrogen bonds, forming a T4(2) motif. They are arranged into a two-dimensional polymeric structure parallel to (10) in which the water mol-ecule is a single donor and a double acceptor, whereas the amino group is a double donor and a single acceptor in the hydrogen bonding. These two-dimensional assemblies alternate with the layers of phenazine mol-ecules arranged into a herringbone motif. Each phenazine mol-ecule is hydrogen bonded to two water mol-ecules and thus a three-dimensional framework of hydrogen-bonded mol-ecules is generated.