Background: The traditional basis of diagnosis is identification of Giardia lamblia trophozoites or cysts in the stool of infected patients. Recently the advent of more objective techniques like antigen detection methods has led to an increase in their use versus those that rely on subjective microscopic examination of fecal specimens for Giardia cysts may facilitate diagnosis of G. lamblia in stool specimens. Methods: Purified G. lamblia cysts antigen was prepared by two-phase sucrose gradient technique. Polyclonal antibody against purified G. lamblia cysts antigen was prepared and labelling with horseradish peroxidase and Nano Magnetic Beads (NMB) to be used as detecting antibody. A total of 72 stool samples, 32 samples positive for giardiasis, 20 samples positive for other parasitic infections in addition to 20 negative samples were examined using dot ELISA and NMB dot-ELISA. Results: The sensitivity of the traditional dot-ELISA was 81.3 % and it increased by using the NMB-dot-ELISA to be 96.9% in stool samples. Specificity of both techniques was 97.5%. The present study concludes that diagnosis of G. lamblia by NMB-Dot-ELISA technique is sensitive, specific, rapid and easy to perform and interpret. In this study, using the nano-magnetic beads increased the sensitivity of the applied technique.