Background: Giardia lamblia, a flagellate protozoa, is a one of the most common causes of non-viral (parasitic) diarrheal illness in humans. Laboratory diagnosis mainly consists of direct microscopic examination of stool specimen for trophozoites and cysts. However, due to intermittent fecal excretion of the parasite, the patient may be misdiagnosed, continue excreting the parasite and infecting others. Therefore, other methods of diagnosis should be looked for, which overcome the drawbacks of microscopy when used alone for diagnosis. The present study aimed to evaluate the efficacy of copro-antigen detection by ELISA test in comparison to direct microscopy in the diagnosis of G. lamblia in stool specimens from patients with diarrhea and other gastrointestinal symptoms. Patients and methods: stool samples were collected form 250 child included in the present study (150 symptomatic and 100 apparently healthy as a control group) aged between 1-10 years old, and subjected for direct microscopic examination and ELISA test for copro-antigen detection. Results: out of 250 stool samples, 53 specimens (21.2%) were positive for Giardia by direct microscopy, while 68 specimens (27.2%) were positive by ELISA test. Conclusion: ELISA test for copro-antigen detection in stool samples is a rapid and effective method with high sensitivity and specificity for diagnosis of giardiasis in stool specimens even when the parasitic count is low, thus reducing the chances of missing even in the asymptomatic cases.