BACKGROUND Chlamydia is gram-negative obligate bacteria which causes a wide variety of diseases in humans and animals. To date, there are a few reports about the seroprevalence of Chlamydia and the risk factors associated with Chlamydia infection in yaks in the world. In this study, 974 blood samples were collected from white yaks (Bos grunniens) in Tianzhu Tibetan Autonomous County, Gansu province, northwest China from June 2013 to April 2014. RESULTS Antibodies against Chlamydia abortus were examined by the indirect hemagglutination (IHA) test, and 158 of 974 (16.22%) white yaks were seropositive for C. abortus antibodies at the cut-off of 1:16. The risk factors associated with seroprevalence were evaluated by a multivariate logistic regression analysis. Region, gender and age of white yak were left out of the final model, due to its insignificance in the logistic regression analysis (P > 0.05). However, season was considered as a major risk factor associated with C. abortus infection in white yaks. CONCLUSIONS To our knowledge, this is the first survey of C. abortus seroprevalence in white yaks in China, which extends the host range for C. abortus and has important implications for public health and the local Tibetan economy.