The purpose of the present study was to investigate the effect of Iranian EFL learners' proficiency level on their self-related personality traits (self-esteem and self-efficacy). To this end, 141 English major students, male and female, studying at Imam Khomeini International University (IKIU) and Kar Non-profit University in Qazvin, Iran were asked to respond to the Rosenberg Self-esteem Test, the General Self-efficacy Scale, the Academic Self-efficacy Scale, and the Self-efficacy for Self-regulated learning Scale. Also, the Michigan Test of English Language Proficiency (MTELP) was administered to determine their language proficiency level. Kruskal-Wallis procedure was used to analyze the data. Based on the findings, no significant difference was found in the participants' self-esteem and self-efficacy across proficiency levels. The results of this study may have theoretical and pedagogical implications for teachers, learners and syllabus designers.