In this study, the effects ofmycorrhizal fungal inoculations of Glomus mosseae, G. etunicatum, G. fasciculatus and Gigaspora margarita species on phenolic compounds and pathogenesis related proteins were investigated in pepper - Phytophthora capsici plant pathosystem. Root colonization by mycorrhizal fungi increased after 15, 25 and 45 days after inoculation depending on the root developmental stage. G. mossea and G. fasciculatus reached the highest root colonization level. In addition, arbuscule formation, spores inside or outside the root cells were observed after 25 and 45 days, respectively. The disease development of pepper plants was decreased depending on the mycorrhizal fungi colonization compared to the pathogen inoculated plants. Total phenolic compounds increased in all treatments as compared to non mycorrized non pathogen treated control, but was highest when plants were inoculated with both, the mycorrhizal fungi and the pathogen. Overall, 12 different phenolic compounds were identified using thin layer chromatography according to Rf. In general, there was an increased in the activity of beta-1.3-glucanases and chitinases after 3, 6 and 9 days as compared to control in stem extracts ofmycorrhizal fungi and or P. capsici treatments. The enzyme activities were higher 6 days after inoculation, but decreased 3 days later in all treatments. In conclusion, increasing activity of phenolic compounds and enzymes were observed depending on simultaneous inoculations with mycorrhizal fungi and pathogen, that could be involved in disease resistance.