The English language is an essential element of the educational landscape of Nigeria. It describes the instrument of effective teaching and learning at every academic level. Consequently, communication in the classroom has been fraught with challenges due to numerous reasons. Thus, the purpose of this present study was to examine English proficiency as a scarcely explored variable that could determine the variation in classroom communication in tertiary institutions. A convenience sample of two hundred and thirty undergraduates (n=230) was randomly selected from Enugu and Anambra states as the respondents. Data for the study was collected using a self-report instrument assessing English proficiency and classroom communication. A linear regression model was performed on the data, and the result revealed that English proficiency is a significant predictor of classroom communication. Thus, it is concluded that English proficiency is an essential determinant of student-teacher classroom interaction. The practical implications are discussed.