Belief is a central construct in every discipline which deals with human behavior and learning (Horwitz, 1985). Also Vocabulary instruction occurs in classrooms every day at a variety of levels and for a variety of purposes. After all, words are the currency of education. The teacher's beliefs about learning will lead them to different strategies based on their beliefs and consequently it will effect on the learners' amount of Learning. The researcher aims at investigating whether such influences are significant regarding learning vocabulary or not. Language teachers' beliefs and understandings of teaching as well as learning play an important role in their classroom practices and in their professional growth. As Harste and Burke (1977) postulated, teachers make decisions about classroom instruction in light of theoretical beliefs they hold about teaching and learning. Teachers' beliefs influence their goals, procedures, materials, classroom interaction patterns, their roles, their students, and the schools they work in. The present study investigates teachers' beliefs as one of the most significant issues in education. The researcher wants to identify which one of the teachers' lexicon teaching beliefs is more effective in enhancing learners' vocabulary intake. The beliefs which are under question in this study are divided into three groups. The first one is Memory-based, the second one is meaning-based and the last one is function-based lexicon teaching beliefs. In this study the researcher concluded that On the basis of the findings, it is possible to make the following statements about learning vocabulary by Iranian EFL learners: 1) The Learners who were taught by teachers with higher level of function-based lexicon teaching beliefs are superior in promoting their lexicon learning to those who were taught by teachers with higher level of meaning-based or memory-based lexicon teaching beliefs. 2) The Learners who were taught by teachers with higher level of meaning-based lexicon teaching beliefs are superior in promoting their lexicon learning to those who were taught by teachers with higher level of memory-based lexicon teaching beliefs. 3) The learners who were taught by those teachers with higher level of memory-based beliefs are in the lowest level of promoting their vocabulary learning in contrast with other groups.