This paper explores the phonological behaviour of Hausa-English bilinguals in their code switching with regard to segmental changes, suprasegmental changes, social triggers and theoretic interpretation. Based on Communication Accommodation Theory and bilingual phonology models, a collection of data was taken using educated bilinguals in Northern Nigeria using recorded conversations in different social situations. The identified segmental changes are persistent in nature, being a movement towards /æ/ → /a/, /ɪ/ → /i/, /θ/ → /t/, and /ð/ → /d/, as well as the shift in prosody more in accordance with English stresstimed rhythm as opposed to that of Hausa tonality. These socially-conditioned shifts are explained by the fact that, when social interactions are formalized, they imply convergence with the standards of prestigious English, but when informal, they remain more strongly influenced by Hausa. The findings can be interpreted to mean that code-switching is a lingual mechanism of being specific in addition to being a sociophonetic mechanism of identity negotiation. The study has a contribution to dynamic interactions of L1 and L2 phonologies in the multilingual societies, and the study creates implications on phonetics,phonology,and sociolinguistics. It is recommended that the research be extended to other Nigerian languages, sample sizes be expanded and use of acoustic analysis to get finer information on prosodies.