ABSTRACT This study is a lexico-syntactic analysis of the influence of Yoruba language on the usage of English among selected undergraduate students of Obafemi Awolowo University, Ile-Ife. Over the years, the coexistence of English language and Yoruba language in the southwestern part of Nigeria has led to code-switching of the two languages by the people who are literate in both languages. This study focuses on how the usage of the indigenous Yoruba language has interfered with the proficien...