ABSTRACT Giardiasis is the most common intestinal parasitic disease worldwide. Clinical presentation ranges from asymptomatic to abdominal pain, diarrhea, and iron deficiency anemia. Treatment modalities include tinidazole, metronidazole, and paromomycin. We present a case of an adult man with anemia and suspected gastrointestinal bleeding who was found to have a duodenal nodule consistent with Brunner gland hyperplasia, and biopsy also showed Giardia . Limited case reports of Giardia diagnosed by duodenal biopsy are found in the literature. To the best of our knowledge, this is the first report of giardiasis presenting as Brunner gland hyperplasia.