Poly[(N,N-dicarboxymethyl)allylamine] as a water-soluble polymeric chelating agent was prepared by carboxymethylation of poly(allylamine) (PAA) with chloroacetic acid or bromoacetic acid. The H-1-NMR, IR, and elementary analyses showed that the iminodiacetic group was introduced quantitatively into the amino group of PAA. Chelating properties of this polymeric chelating agent toward Cu2+, Ni2+, Zn2+, and Ba2+ were examined by potentiometric titration.