Hexane, dichloromethane, ethyl acetate, acetone and methanol extracts of the thalli of Parmotrema praesorediosum (Nyl.) Hale was tested for their antimicrobial activity against eleven human pathogenic microorganisms using standard disc diffusion method. The potential secondary metabolite constituents of ethyl acetate and dichloromethane extracts were active against the microorganisms viz., Bacillus cereus, Corynebacterium diptheriae, Shigella flexnerii, Staphylococcus aureus, Vibrio cholerae and Candida albicans. Solvents treated discs were used as negative control and discs treated with standard antibiotics served as positive controls in the experiment. The dichloromethane extract exhibited potential antibacterial and antifungal activity.