Many researchers examined the role and importance of vocabulary in language teaching and learning. For example, laufer (2006, 2010), Nation (2001) and Qian (1996) are some of the researchers who work on the role of vocabulary, context and translation. This paper aims at discovering and investigating the effect of L1 translation, L1 gloss and context on vocabulary learning on EFL Iranian learners. A total number of 120 EFL students in private English institutes in Sari participated in the present study. They were divided into two proficiency groups and three learning contexts. In order to make a list of words unknown to the learners the participants were given a list of 40 English words extracted from the passage and they were asked to write their equivalents in L1. As a result of this examination 20 target words were selected to be worked on. The treatment session happened a week after the pretest. According to the results, there is relationship between effectiveness of method and proficiency level of the learners. Based on statistical calculations and our findings, contextual methods of vocabulary learning is best appropriate for high proficiency learners and translation methods best suited low proficiency group. This study can be of high value for language teachers especially in public schools because they can use translation techniques for weak students and contexts along with gloss for students with higher level of English proficiency. This study can be useful for institute and private institutes too because language teachers can also use translation and context to improve the word knowledge of their students.