Changes in some of defense compounds such as peroxidase enzyme activity and amount of total phenol in treated Golden Delecious apple fruits with an antagonist isolate of Pseudomonas fluorescens (isolate F7) and Penicillium expansum, the cause of blue mould was studied. Extraction and measurement of peroxidase enzyme activity and total phenol was performed in 3, 6, 9 and 12 days after inoculation of the fungus. Results showed that in simultaneously inoculated apple fruits with the bacterium and pathogen, peroxidase enzyme activity and total phenol increased significantly as compared to the control. Maximum peroxidase enzyme activity and total phenol were recorded nine days after inoculation of fungus. Results suggested that increase in peroxidase enzyme activity and total phenol can be attributed to induction of the defense compounds in apple fruits by P. fluorescens isolate.