Synthesis of novel aliphatic biodegradable copolyesters namely Poly(ethylene sebacate-co-propylene succinate) and poly(ethylene sebacate-co-propylene adipate) were carried out using Poly(Propylene Succinate), Poly(Propylene Adipate) and Poly(Ethylene Sebacate) in presence of Poly Phosphoric acid. Synthesis of Poly(Propylene Succinate),Poly(Propylene Adipate) and Poly(Ethylene Sebacate) were carried out using respective diols and diacids in presence of titanium tetrabutoxide as catalyst. Newly synthesized copolyesters were characterized by solubility studies, viscosity measurements, thermal analysis, IR Spectroscopy and Nuclear Magnetic Resonance Spectroscopy (1H-NMR and 13C-NMR). The characteristic peaks present in the homopolyesters were recorded in the copolymers as well. DSC analysis of the copolyesters showed that the introduction of methylene units in the di-acid decreased the Tm and Tg.