Although knowledge of intestinal parasites predates Hippocrates, the Hippocratic Corpus provides the first scientific observations about the clinical perception and treatment of helminthic diseases. These observations follow the scientific principles of Hippocrates, the father of modern medicine, who relied on knowledge and observation. This article is based on a systematic study of the Hippocratic texts, and presents observations on diseases caused by intestinal parasites with respect to regularity of appearance, patient age, symptoms, and treatment. Three types of helminths are described: “helmins strongyle” (roundworm), “helmins plateia” (flatworm), and “ascaris” (which corresponds to Enterobius vermicularis). Helminthic diseases primarily appear during childhood, well after teething. The described systemic symptoms include weakness, sickness, discomfort, tiredness, anorexia, and emotional instability; gastrointestinal symptoms include change in bowel movements, vomiting, and colic pain in the epigastrium. We identified several accounts of cases of helminthic diseases in the Hippocratic texts. Of particular interest are the descriptions of a helminth emerging from a fistula in the navel region and the surgical treatment of helminthic diseases, reinforced by being described on a dedicatory inscription at the Asclepion in Epidaurus. We finally encountered the use of powerful purgatives as antihelminthics, which have been widely used, even into the 21st century.