The present study investigated the impact of systemic-theoretical instruction (STI) on Iranian EFL learners’ English Passive Structure formation. In such doing, first, an Oxford Placement Test was administered among 12 Iranian EFL language learners studying in Iran. Based on the OPT scores, 50 out of 68 participants were randomly selected and divided into two equal experimental and control groups. As the main treatment, Concept Based Instruction (CBI) principles, was taught twice a week, and lasted eight weeks. At the end of the treatment, a posttest on English Passive structure with the similar content as the pretest was given to the learners, and the results were analyzed through independent sample t-test. The findings revealed that there was a significant difference between two groups’ performance in learning passive structure in posttest. In fact, the experimental group outperformed their counterparts in the control groups in terms of English Passive structure learning. Finally, the pedagogical and theoretical implications of the study were presented.