This work is based on the findings of a study carried out in a Form One History class on Effects of Using English on Classroom Interaction.Data collection was done through classroom observations and interviews with students and the teacher of History. Findings from the study revealed the challenges encountered by both students and their teacher causing them to resort to different coping mechanisms. Participation in class activities were found to be dominated by a few students who did their primary education in English medium schools. The study concluded that incompetence in the MOI is an obstacle to classroom interaction and recommended that English teaching and its use in Tanzanian classrooms be initiated early enough in schooling.