Most previous studies on discourse markers (DMs) have yielded a common finding, that is, native speakers of English (NSs) and nonnative speakers of English (NNSs) use discourse markers in different ways, especially as regards frequency of occurrence, position and function. Although discourse markers, such as I think, I mean and you know, are sometimes syntactically peripheral and poor in semantic meaning, they are pragmatically indispensable in spoken discourse and serve a variety of pragmatic functions. This study focuses on one of the most frequently overused discourse markers by NNSs, I think, and presents a comparative analysis of I think as used by Hong Kong English (HKE) speakers and British English (BrE) speakers in terms of its frequency of occurrence, position, collocation patterns and pragmatic functions, based on two parallel corpora: the Hong Kong component (ICE-HK) and the British component (ICE-GB) of the International Corpus of English (ICE). By highlighting similarities and differences in the use of I think by HKE and BrE speakers, this study also examines possible reasons that may lead to these.