Green synthesis is becoming increasingly important as an eco-friendly alternative to the traditional production process because of its growing industrial applications. In this study, peroxidase enzymes of the leaf extracts of the plants Ficus carica (Fig) and Euphorbia amygdaloides (Euphorbia) were used for the synthesis of gamma-Fe2O3 nanoparticles (NPs). The structural, morphological and methane gas sensing properties of gamma-Fe2O3 NPs were investigated. gamma-Fe2O3 NPs obtained from the Fig plant peroxidase enzyme showed a higher response, selectivity and short response/recovery time than gamma-Fe2O3 NPs obtained from the Euphorbia plant peroxidase enzyme, which exhibited 15% response to 1-ppm methane gas at 150 A degrees C. Impedance spectroscopy analysis showed that the resistance due to the grain boundaries significantly contributed to the characteristics of gas sensing. It can be seen from results that gamma-Fe2O3 NPs produced from peroxidase enzymes that purified from Fig plant have great potential for industrial applications.