The aim of this study was to investigate the potentiality of cell phone use in the EFL classroom of Bangladesh as an instructional tool. The researcher conducted a case study on Jahangirnagar University of Bangladesh. For the study, some SMS based class tests were conducted in the English Department of the university where one hundred undergraduate EFL students participated as subjects. Before the tests, Some EFL teachers sent mobile SMS to students as a means of instruction for teaching appropriate use of preposition for one week. After one week, the teachers took some class tests where the test questions were delivered via SMS and the students also answered the test questions by mobile SMS. The author collected data through students' questionnaires, and teachers' interview records and classroom observation reports. The research results demonstrated that cell phone has great potential as an instructional tool despite some challenges that can be resolved by the sincere attempts of the authority, teachers and by changing the ethical point of view that consider cell phones as merely a disturbing factor in the classroom.