Symbiotic fungus Piriformospora indica has useful and unique features to enhance growth and resistance of plants against biotic and abiotic stresses. In the present study the effects of this endophyte fungus on the growth and activities of antioxidant enzymes in medicinal plant Atropa belladonna were studied. After co-existence, the effect of fungus on plant growth, total protein content and the activities of ascorbate peroxidase (APX, EC 1,11,1,11), catalase (CAT, EC 1,11,1,6) and peroxidase (POX, EC 1,11,1,7) enzymes were determined using a spectrophotometer. The results showed an increase<span style="font-family:;" dir="RTL" new="" b="" lotus";="" roman";"="" "times="" roman";=""> on the growth parameters, and total protein content in root, stem and leaf of inoculated plants in compare to control. Inoculation by endophte fungus increased the total fresh weight of plantlets by 1.87-fold and shoot height by 2.11-fold. The presence of P. indica decreased all three enzyme activities in the stems and leaves, whereas it increased enzyme activities of CAT, APX and POX in roots by 2.2-, 2.3- and 2.5-fold, respectively, in comparison with control plants. We conclude that this fungus can be used to increase plant growth and as bio-material protection tool via increasing root antioxidant enzyme activities in important medicinal plant Atropa belladonna.