Diplolepis fructuum (Rubsaamen, 1895) (Hymenoptera: Cynipidae) is one of the important insect species that causes damages on Rosaceae species. With this study commenced in 2018 at the laboratory of Department of Biochemistry, Faculty of Science, Cumhuriyet University to get a biochemical data, an esterase (EC 3.1.1.X) from the larvae of D. fructuum was purified using Q Sepharose anion exchange, phenyl Sepharose CL-4B and Sephacryl S100 HR gel filtration chromatography, respectively. The enzyme had 6.94 U/mg protein specific activity, about 29-fold purity, and 8.8% yield. Only one activity band was observed in native-PAGE studies. The molecular weight of the esterase was estimated as 60 kDa using native-PAGE and SDS-PAGE techniques. By the kinetic data, optimum temperature and pH for the enzyme was determined as 40 degrees C and 9.0, respectively. The enzyme was stable for 4 h at 40 degrees C and pH 8.0. K-m and V-max values were found to be 0.035 mM and 1.41 mu mol/mL.min., using 4-nitrophenyl butyrate (p-NPB) as substrate. The enzyme exhibited its highest activities on p-NPB (100%) and 4-nitrophenyl acetate (52%). All of these data indicate that the enzyme might be a typical esterase with different kinetic properties and molecular weight than esterolytic enzymes reported from other insect species.