This study investigates code-switching observed between Arabic and English at university level in Iraq. The hypotheses and objectives of the empirical data collection are presented along with a linguistic analysis on the phonological, morphological, lexical, and syntactic levels. Suggestions are advanced about when, how and why code-switching occurs, emphasising the social variables of topic, participants, and situation, as well as psychological and academic constraints. Finally, some conclusions are drawn and some recommendations made for further studies in this area.