A new thallium (I) coordination polymer [Tl(PsucH)]n (PsucH = phenylsuccinic acid) has been synthesized and characterized by single crystal X-Ray analysis, elemental analysis and IR spectroscopy. The single crystal X-Ray analysis shows that this polymer is 2-D along a axis. Flower-like nanostructure thallium (III) oxide, Tl2O3 has been prepared by direct thermal decomposition of thallium (I) coordination polymer. The nanostructure was characterized by scanning electron microscopy (SEM), X-Ray powder diffraction (XRD) and IR spectroscopy. The thermal stability of the Tl2O3 nanostructure was studied by thermal gravimetric analysis and differential thermal analysis (TGA /DTA) too.