This paper sets out to examine the phonological interference in the spoken English performance of the Izon speaker. It emphasizes that the level of interference is not just as a result of the systemic differences that exist between both language systems (Izon and English) but also as a result of the interlanguage factors such as the level of the individual’s interaction in and with the L1, his level of education and access to oral English lessons while in school. The research reveals some troublesome contrasts in the two languages. The three factors that determine the level of interference are: the level of immersion of the individual in Izon; the level of the individual’s education; the individual’s oral English education exposure. The English language teacher has to be aware of these factors and pay particular attention to the differences in the phonological systems of the first language (L1) and the second language (L2) which can cause interference.Keywords: Mother-tongue, First language, Second language, Interlanguage, and Immersion