1. In this study, the effect of chlorogenic acid extract from Lonicera japonica Thunb. on Mycoplasma gallisepticum infections and the performance of broiler flocks was investigated. 2. A total of 360 Ross-308 broiler chicks taken from M. gallisepticum seropositive flocks were divided equally into three groups designated as control (nothing administered), antibiotic (Tylosin tartrate given for the first 3 d and d 20-22) and test group (chlorogenic acid extract given twice a day on d 16 and 22). 3. Broiler performance analysis, serological tests (slide agglutination), molecular identification (polymerase chain reaction) and histopathological examination were performed to detect M. gallisepticum. 4. The results show that chlorogenic acid not only increases live body weight but is also an alternative treatment option in M. gallisepticum-infected broiler flocks.