Heartworm disease is caused by Dirofilaria immitis in dogs and cats. Dirofilariasis is clinically considered very important, because of its severe and life threatening disease in case of even light infection. Cats are infected much less commonly, even in areas which present heavily infected dogs. After clinical examination blood samples were collected from 120 companion and stray adult cats in Ahvaz city. Dirofilaria microfilaria was detected by modified Knott method and its antigen detected by immunochromatography. One (2.5 years old), out of 120 (0.83%) of the studied cats was infected with Dirofilaria immitis microfilaria. Companion male cat of domestic short hair (DSH) breed. This survey is the first report on isolation of Dirofilaria immitis in cats of Ahvaz city. It seems that carrier mosquitoes and their reservoirs present in this distinct: Therefore continuous challenge for eradication of stray cats and dogs, prophylactic treatment and accurate training to people should be done.