The current investigation was carried out to evaluate the prophylactic and therapeutic effects of allicin against goats experimentally infected with Escherichia coli (E. coli).Twelve native breed goats, one year old, belonging to the private farms of Faculty of Veterinary Medicine, Zagazig University, Egypt, were used in this study. The animals were divided into three groups (4 goats each); prophylactic group (G1) received allicin “2.7 mg/kg twice daily” then infected with E. coli, treatment group (G2) was experimentally infected with E. coli, then received the above mentioned allicin dose and lastly untreated control group (G3) were remained without any interference. All goats were exposed to complete and comprehensive clinical examination. Blood samples were collected from jugular veins of goats to determine blood pictures and some selective parameters. Clinical investigation of goats revealed a significant increase of mean rectal temperature, heart and respiration rates on the 7th day in G2 till the 28th day. Hematological analysis showed that oral administration of allicin had no significant effect on the hematological parameters, hemoglobin (Hb), red blood cells (RBCs) and packed cell volume (PCV). A significant increase in white blood cells (WBCs) and neutrophils on the 7th , 14th , 17th and 28th days in both treated groups was observed. Biochemical analysis showed significant increase of malondialdehyde (MDA) levels in both groups following E. coli inoculation then decreased significantly till retuned to the normal range on the 28th day. Total antioxidant capacity (TAC) was increased significantly on the 7th day in G1 but it significantly decreased in G2 during the same period then increased significantly on both groups till the 28th day. Immunological results showed marked increase in both research treated groups. Allicin administration increase the release of interleukin-6 (IL-6), interleukin- 12 (IL-12) and tumor necrosis factor-alpha (TNF-α) in both infected groups than in the untreated control one.