Methyl parathion hydrolase (MPH) is an important enzyme in hydrolyzing toxic organophosphorus (OP) compounds. However, MPH is easily deactivated when subjected to extreme environmental conditions and is difficult to recover from the reaction system for reuse, thereby limiting its practical application. To address these shortcomings, we examined the entrapment of MPH in an environment-friendly, biocompatible and biodegradable cross-linked poly(gamma-glutamic acid)/gelatin hydrogel. The cross-linked poly(gamma-glutamic acid)/gelatin hydrogels were prepared with different gelatin/poly(gamma-glutamic acid) mass ratios using water-soluble carbodiimide as the cross-linking agent. The MPH-entrapped cross-linked poly(gamma-glutamic acid)/gelatin hydrogel (CPE-MPH) not only possessed improved thermostability, pH stability, and reusability but also exhibited enhanced efficiency in hydrolyzing OP compounds. Furthermore, CPE-MPH possesses high water-absorbing and water-retaining capabilities. We believe that the cross-linked poly(gamma-glutamic acid)/gelatin hydrogels are an attractive carrier for the entrapment of diverse enzymes, affording a new approach for enzyme entrapment.