Poly(α-methyl β-propiolactone) (PmPL) was synthesized through anionic ring-opening polymerization of the corresponding lactone. Structural characterization of PmPL was performed by using FTIR, 1H-NMR and MALDI-MS spectrometry. Thermal behavior of the polymer was investigated by using DSC and TGA. Glass transition, melting and thermal degradation temperatures of PmPL were determined as -36.7, 95.5 and 242.4°C, respectively. Biodegradation studies were conducted at 37°C in three different media, that is, pH 7.4 phosphate buffered saline (PBS), PBS containing pancreatic trypsin and PBS containing pancreatic lipase. The biodegradation kinetics and mechanism of the polymer were followed by gravimetric measurements and LC-MS analysis. Up to 65% mass loss in 5-week period was recorded for the buffer media in the presence of lipase and trypsin. LC-MS analysis of the residues in the media revealed that biodegradation undergoes mainly through ester bond hydrolysis.