Giardia lamblia is considered one of the most common intestinal pathogens worldwide which cause gastroenteritis in human and animal. The purpose of the present study was to determine the prevalence and the most genotype that common of G. lamblia in the Wasit province, Iraq. A total of 50 stools samples have been collected from patient’s that suffering from severe diarrhea from hospitals Al-Zahraa and Al-Karama in Wasit province, Iraq during the period from May 2016 to September 2016. The results showed 36 (72%) was positive, while 14 (28%) was negative by Nested PCR technique. Then amplification by Nested PCR has been made to observe the most genotype frequent which common, the results showed 8 (22%) contained genotyping A genotyping and B 28 (78%) contained genotype B. In this study molecular techniques played a significant role in the detection, epidemiological reconnaissance and outbreak studies.