Coxiella burnetii is the causative agent of Q-fever, a widespread zoonosis. In domestic animals infection remains either asymptomatic or presents as infertility or abortion. Clinical presentation in humans can range from mild flu-like illness to acute pneumonia and hepatitis. In humans serology is the gold standard for diagnosis but is inadequate for early case detection, so real-time PCR and nested-PCR assays were developed in this study to measure amounts of C.burnetii shed in milk. Our study was to assess the sensitivity of the realtime PCR and nested-PCR for detection of Coxiella burnetii in bovine bulk milk samples from dairy herds in 3 provinces (Chaharmahal and Bakhtiari , Isfahan and Yazd) of Iran. In the present study, 300 bulk milk samples from 89 dairy cattle herds were tested for C. burnetii using real-time PCR and nested-PCR assays. The animals which their milk samples collected for this study were clinically healthy. In total, 74 of 300 (24.7%) cow milk samples were positive in real-time PCR assay and 26 of 300 (8.7%) samples were positive in nested-PCR assay. McNemar test shows a significant difference in detection of C. burnetii between real-time PCR and nested-PCR. Also the results of this study indicate those clinically healthy dairy cows are important sources of C. burnetii infection in Iran.