This is an experimental trial to prepare a vaccine from gamma-irradiated Giardia lamblia which is evaluated in experimental animals. The study was conducted from December 2015 to April 2016. The field survey of the parasite was conducted from those patients attending the laboratories of the Alawi Children's Hospital in Rusafa and the Al-Yarmouk Teaching Hospital in Karkh, through which 1250 stool samples of different age groups were examined. Five groups of mice were used in the study; the first was injected with normal saline and considered as a negative control group, the second was injected with cystic form of non-irradiated Giardia lamblia and considered as a positive control group, whereas the other three groups were injected with gamma irradiated Giardia lamblia at three different doses 10, 15 and 25 rad respectively. Giardia lamblia was primarily cultivated in liver infusion agar for ten days to obtain the active phase. On the sixth day, the cystic phase was purified and standardized to be used in the infection of mice with or without the exposure of gamma rays. Mice showed high sensitivity to parasitic infestation, in the gamma non-irradiated and the irradiated with gamma 10 rad, and 15 rad irradiated groups which was 100%. The results expressed an excystation process of the depleted phases and the release of the feeder phases. The results of the three irradiated groups consisted of histopathological changes of the small, and the rectum by dissection after two weeks of infection, with intestine amputation lesions, as well as ulceration and inflammation of the inflammatory cells represented in small numbers of neutrophil, lymphocytes, and eosinophils. The presence of ulceration and fall of epithelial cells in the intestinal cavity has been shown, and different forms of the parasite have been observed. Mice which was injected with irradiated G lamblia at high dose (25 rad), not show and sensitivity to the challenge infection and no excystation of thy parasite had been done. After 2 wreaks, a comparison was achieved between all study groups in which no histopathological changes were noticed in the mice irradiated with dose of25 rad. After another two weeks, a challenge dose was given (un-attenuated G lamblia) and mice were dissected after another two weeks, no changes on the level of histopathology of intestinal tissue were noticed the results suggested that mice acquire an immunity against the parasite infection.