The effect of dictionary usage on English as a foreign language (EFL) test performance is a controversial topic. Teachers generally regard both monolingual and bilingual dictionaries as necessary tools for effective reading comprehension. Students of EFL are expected to know how to use bilingual dictionaries without specific guidance (Marsha Bensoussan & Donald Sim, 1984).This study aimed to explore the impact of the use or non- use of bilingual dictionary on reading comprehension performance and word power improvement of Iranian EFL learners in Kerman Azad University. 80 English students studying at Kerman Azad University who had taken reading comprehension course in the academic year 2016-2017 were randomly selected for the purpose of this study. The instruments used to collect the required data were an attitude questionnaire to evaluate learners' attitudes, and the students' scores to evaluate their reading comprehension performance. After filling the questionnaires by leaners, the collected data were analyzed by using SPSS tools. Also, an interview with some of the learners was done to determine learners' attitudes toward bilingual dictionary. The findings of the study demonstrated that using bilingual dictionary had positive effect on reading comprehension performance of EFL learners.