In the title compound, C(17)H(14)N(4)O(2)·1.5H(2)O, the mean planes of the pyridine ring and quinoline group make a dihedral angle of 21.0 (2)°. One water molecule lies on a twofold rotation axis. The organic mol-ecules and the three water mol-ecules are linked into infinite chains by N-H⋯O, O-H⋯O and O-H⋯N hydrogen bonds.