Parametric optimization for the enhancement of mechanical properties and biodegradability for LDPE blended silane-modified nanosilica films with different compositions of starch/starch phthalate has been studied by central composite design approach of response surface methodology. The effect of thickness of the films on the biodegradability and the applicability range has been analysed. Statistical analysis of the mechanical degradability and biodegradability in both garden soil and vegetable waste environments was tested. The results obtained suggest that at a starch content of 10% and a thickness of 586.192 and 350 micron the maximum tensile and tear strength of 11.71 MPa and 210.31 N/mm could be achieved, whereas for modified starch film, 30% biofiller content and 495.38 micron thickness showed the maximum tensile (12.401 MPa) and tear (215.137 N/mm) strength. Biodegradability of the films was found to be maximum (14.80% for starch and 15.74% for starch phthalate films) in garden soil for 350-micron film containing 30% starch/starch phthalate content. The optimized conditions suggest the optimum thickness and biofiller content are required for high biodegradation and superior mechanical properties.