Objective: study was conducted to determine the prevalence and incidence of Giardia lamblia parasite between human and cows in Basrah province with comparitives. Design: During research collected 1344 stool samples from human and 1049 stool samples from cows from September 2012 to May 2013. All samples collected in sterilized cups, then examined under microscope by conventional microscopic methods and concentration methods. Results: In human, 405 cases were infected 30.1% and 322 positive cases have been recorded in cattle 30.6%. The study was shown that all age groups are susceptible to the disease. Also in this study recorded different ratios of giardiasis during months of year. Conclusion: The study recorded high prevalence of giardiasis in Basrah province. Giardiasis was widely distributed throughout the months of study. Many factors could affect prevalence of giardiasis in human as socio-economic status, overcrowding, level of education, sanitation, contact with animals and types of water source.