Giardia is a protozoal organism that is an important cause diarrhea in pets. The organism commonly infects pets (and people) drinking from contaminated water sources. Pets with Giardia may be asymptomatic; younger and debilitated pets may have severe diarrhea and dehydration. Diagnosis of Giardia can be challenging as the organisms are not always shed into the feces to be detected. Multiple stool checks may be necessary before a definitive diagnosis can be made. Treatment for Giardia includes supportive care with fluids to rehydrate; bland, easily digested diets; and an oral medication to eliminate the infection. To prevent reinfection, 1) bathe your pet during treatment to remove any organisms attached to the fur, 2) treat all pets in the household, and 3) pick up feces as soon as possible to prevent environmental contamination. Some strains of Giardia can be transmitted from your pet to people. Contact your physician if you or a family member suspects a Giardia infection.