A new terbium(III) sensor based on 1, 3-Diaminopropane-N,N,N',N'-tetraacetic acid as a suitable ionophore is described. The electrode comprises 3% ionophore, 30% PVC, 65% NB and 2% NaTPB. The sensor has a linear dynamic range of 1.0×10−8 to 1.0×10−2 M with a Nernstian slope of 19.8±0.4 mV per decade and a detection limit of 8.4×10−9 M. In this study, potentiometric selectivity coefficients, describing the preference of the membrane for terbium ions relative to an interfering ion, were determined by the matched potential method (MPM). The proposed sensor shows a very good selectivity towards a large number of cations, such as Yb(III), Gd(III), Eu(III), Ho(III), Tm(III), Fe(III), Na(I), K(I), Ca(II), Mg(II), Zn(II), Co(II), Cd(II), Ni(II) and Pb(II) in comparison with former ones. It was used as an indicator electrode in the potentiometric titration of Tb(III) ions with EDTA. The sensor was applied to the determination of Tb(III) ions concentration in water samples solutions.