In the title complex, (C(10)H(9)N(2))[Pr(C(6)H(2)N(2)O(4))(2)(H(2)O)(5)], the Pr atom is nine-coordinated by nine O atoms from two pyridazine-4,5-dicarboxyl-ate anions and five water mol-ecules. It is noteworthy that there is a protonated bipyridine mol-ecule in the structure. Inter-molecular O-H⋯O, O-H⋯N and N-H⋯N hydrogen bonds are present, resulting in a three-dimensional network.