In the present study, ring opening polymerization of ε-caprolactone was performed by a novel enzymatic catalyst, Candida antarctica lipase B (CALB) immobilized on a modified silica-based material by physical adsorption. Molecular weight distributions and chain structures were compared by using gel permeation chromatography (GPC) and hydrogen nuclear magnetic resonance ( 1 H NMR) analysis, respectively. In addition, for the determination of thermal properties, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed. Scanning electron microscopy (SEM) was applied to observe the surface structure of the polymer. Effects of temperature, reaction time, and enzyme concentration on molecular weight of poly (ε-caprolactone) (PCL) were investigated and optimum conditions for the ring opening polymerization of ε-caprolactone via this new immobilized enzyme were obtained. Highest molecular weight was achieved as 14000 g/mol at the end of 48 hours at 60 ÌŠ C. Moreover, considerably high molecular weights were successfully reached at lower temperatures by this novel enzyme, which makes this process low energy consuming besides being environmentally friendly. It is suggested that, CALB immobilized on a modified silica-based material by physical adsorption may be a great alternative for widely used commercial enzyme, Novozyme 435. This work also makes possible a new route for polymer synthesis.