A poly(vinyl chloride) (PVC)-based membrane sensor for Tb3+ ions was prepared by employing 1, 3-Diaminopropane-N,N,N',N'-tetraacetic acid (APTAA) as an ionophore, sodium tetraphenyl borate (NaTPB) as an anion excluder, and dibutylphthalate (DBP), benzylacetate (BA), acetophenon (AP) and nitrobenzene (NB) as plasticizing solvent mediators and investigated as a selective membrane sensor. The sensor displays a linear dynamic range between 1.0×10−8 and 1.0×10−2 M, with a nice Nernstian slope of 19.8±0.4 mV per decade and a detection limit of 8.4×10−9 M. The proposed sensor displays a fast response time (~5 s). The potentiometric response is independent of pH in the range of 2.1–9.5.