Abstract: Members of the passerine family Sylviidae are distributed widely around the Old World and the phylogenetic relationships of many species still remain controversial. In this study, we investigated the phylogeny and relationships among 37 species of 11 genera by analyzing DNA sequences obtained from the complete mitochondrial cytochrome b (cyt b) and partial cytochrome oxidase I (COI) genes. The data were analyzed by maximum-likelihood analysis and Bayesian inference. The results demonstrate that the current genus Phylloscopus is non-monophyletic, while Seicercus is synonymized with Phylloscopus or is a group within the genus Phylloscopus. We may conclude that within Phylloscopus there are close relations between P. magnirostris and P. borealis; among P. proregulus, P. yunnanensis, P. pulcher and P. maculipennis, as well as among P. occisinensis, P. schwarzi, P. armandii, P. collybita and P. fuscatus. Monophyly of the genus Cettia could not be corroborated; it is closely related to the genera Abroscopus and Tesia. However monophyly of Acrocephalus is supported. Furthermore, the close relationships between Sylvia and Zosterops and among Prinia, Orthotomus and Cisticola are also supported.