Code- switching is common among people speaking one mother tongue, living in another culture. This paper looks at the purposes of code-switching, what word classes are switched and how often they are switched. A case study was carried out to examine the code-switching in conversations of an Australian-Vietnamese who has a quite complicated educational and social background. Data for the study were collected from three natural conversations and an informal interview. Findings shows various reas ons why she code-switched, with whom she code-switched and how often she did it as well as which part of a sentence she switched
