Beliefs form part of the process of understanding how teachers shape their work which is significant to the comprehending of their teaching methods and their decisions in the classroom. Teachers’ beliefs have been an interesting topic for researchers due to the input they provide for the improvement of English language teaching and learning. Teachers’ beliefs have a deep impact on their classroom principles. The realization of this relationship is very important for teachers to prepare and implement their new syllabus. Teachers’ beliefs affect what they accomplish in their classroom, their attitudes, and their learner’ beliefs. They guide teachers to adopt their teaching strategies for coping with their teaching challenges, shape language learners’ learning environment, their motivation and their language ability. In this study, the researchers define the term belief, explain the nature of teachers’ beliefs, express sources of teachers’ beliefs, and finally mention some previous studies on teachers’ beliefs. The review of related literature revealed that investigating teachers’ beliefs will help them change their methods to teaching and learning over time in order to bring about more improvement for language learners.