The study investigated roles of code switching in mult ilingual public primary schools in Ile-Ife, Nigeria. It also determined the effects of the languages used on teaching and learning mathematics with a view to presenting code-switching as a viable mediu m of instruction to facilitate the develop ment of literacy in ch ildren. The data for the study were obtained fro m five mathematics teachers and fifty pupils from five purposively selected primary schools through ethnographic observation and structured interviews. Data co llected were analysed using Myers-Scotton’s Matrix Language Framework model, as well as descriptive and inferential statistics. The results showed that teachers in the schools used code switching, where Yo ruba was the matrix language and English was the embedded language, as a communicative strategy in their classrooms. Code-switching was also found to be used as an approach to the acquisition of literacy in that it allo wed each pupil to use each of his/her languages in a natural, meaningful way as the various classroom activ ities were being implemented. The study concluded that the use of code switching in mu ltilingual mathemat ics classrooms does not result in a deficiency in learn ing, but is a useful strategy in classroom interaction and efficient way of transferring knowledge to students. In this case, one language might help the other, and sometimes both together may create a new idea, image, thought, behaviour, outlook, organizat ion, and adaptation.