In this study, endoglucanase (EG) from local isolate Aspergillus fumigatus HBF356 was produced and purified using ammonium sulfate precipitation, gel filtration chromatography, and ion-exchange chromatography. The molecular weight of the pure EG was determined as 95 kDa. The optimum pH of the purified EG was determined as 4.0 and the optimum temperature as 60 degrees C. It has been observed that the enzyme had a very high thermostability and preserved 75.8% of its activity after 240 hours of incubation at 50 degrees C. At the same time, the effect of veterinary drugs (gentamicin sulfate and enrofloxacin) on the activity of the EG was investigated. The activity of EG was inhibited by gentamicin sulfate while that was activated with enrofloxacin. The results of this study can give information about the potential of EG from Aspergillus fumigatus HBF356 using as a feed additive and its interaction with animal drugs.