Giardia lamblia is an intestinal protozoan parasite causing diarrhea in humans and some other mammalians world-wide. Giardia infects about 2% of the adults and 6 to 8% of the children worldwide and is currently responsible for the largest number of water-borne outbreaks of diarrhea. There are a variety of agents used for treatment of Giardiasis caused by G. lamblia, which may have various effects. Podophyllotoxin is a non-alkaloid compound from lignan family that has been used as an anti-viral, antifungal and anti-cancer agent. Here we have used PTOX against Giardia lamblia to evaluate its effect as an anti-parasite compound. We have shown that PTOX can inhibit growth of G. lamblia and causes death, suggesting that PTOX can be used against G. lambia.