The present study aimed to investigate of reaction time in terms of phoneme recognition: A comparative study among Iranian Upper-Intermediate vs. Advanced EFL Learners at Institute level. The main question this study tried to answer was whether there is no difference in reaction time in terms of phoneme recognition in Iranian learners at Institute level. To answer the question, 5Upper-Intermediate EFL learners vs. 5 Advanced EFL learners participated in the experiment of the study. They were randomly selected from among a population of 50, both female and male, aged ranged 18-35 via an OPT test scores. They were then divided into groups of 5 and assigned to Upper-Intermediate group vs. Advanced group. A phoneme recognition test was administrated to both groups, then, they choose the correct pronunciation of each word at a definite time. The researcher preferred to use Independent-Samples T-test between the posttest of scores of the study. The researcher applied descriptive statistic to analyze data. The results indicated that Iranian Advanced EFL learners received higher scores vs. Upper-Intermediate EFL learners in terms of L2 phoneme recognition تفاصيل المقالة