The protozoan is a unicellular animal, most are very small many are somewhat larger in size. The tissue protozoa are one of the main determinative factors affecting animal health which cause serious economic losses among farm animal industry all over the world, especially at production time. At the same time, the infected animal meat may serve as an important source of infection to man during handling or if consumed undercooked. The protozoa in animal tissue in this review are classified into 1- blood and tissue protozoa (Trypanosoma, Leishmania, Sarcocystis, Toxoplasma, Neospora, Hammond, Besnotia, Babesia, and Theileria.), 2- intestinal and urogenital protozoa (Entamoeba, Balantidium, Giardia, Trichomonas, Eimeria, Cryptosporidia and Isospora). The identification of particular protozoa in this manual is based on morphological details and life cycle, histopathological studies, bioassay, serological assay, and immuno-histo-chemistry. Ultra-structure and molecular biology also hadbeen included.