The current study was conducted to diagnose the Marek's disease in naturally infected Gallus gllusdomesticus chickens and Brahma chickens in Basrah province , Iraq, on the basis of clincopathological findings and  by Polymerase chain reaction (PCR) . Suspected samples were collected randomly from different areas in Basrah province, (poultry houses, veterinary clinics, markets and Consulting clinic of the veterinary medicine college  of Basrah university). The results of this study showed that some birds had significant  clinical signs of  Marek's Disease, like paralysis of the legs and wings. Post mortem inspection showed different lesions according to chickens species  in the Gallus gallusdomestics which were severely affected in sciatic nerve inferred  by enlargement of sciatic nerve, splenomegaly & hepatomegaly with nodular tumor as well as  lesions in the other  organs. In Brahma chickens there were mild  gross lesions in viscera and  only showed  enlargement of sciatic nerve. Histopathological examination showed  changes in the spleen (necrosis in the white pulp  and hyperplasia in the central arteriole of the white pulp) . Sciatic nerve showed edematous fluid in the nerve parenchyma and infiltration of mononuclear inflammatory cells mainly lymphocytes in the nerves parenchyma. The feather follicleshowed marked vaculationof the epithelial layer as well as infiltration of inflammatory cells in the follicular lining. The confirmation was doneby PCR which showed that the total positive samples for avian Marek's Disease serotype-1 were nine samples,three positive samples of spleens and two positive samples of feather follicles as well as three positive samples of sciatic nerve and one positivesample of liver . Based on these results , MDV was concluded to be the etiology for  this pathological condition in Iraqi backyard flocks. This is the first report of the presence of the MDV in Gallusgallus  and Brahma breed in Iraq. Accordingly, the commercial poultry population in Iraq is not far from the threat of the MDV, and surveillance for MDV is needed.