Knowing how to think about the language learning process is conducive to effective learning especially in the case of grammar structures. Metacognition, a concept derived from cognitive psychology, can assist learners in this case. With regard to young adolescents at lower proficiency levels, there is a long-standing debate on whether to use L1 for teaching metacognitive strategies since learners might not be efficient enough in terms of understanding the concept of metacognition. Therefore, this smallscale experimental study focused on the effect of grammar instruction through the metacognitive intervention delivered in L1 on the EFL pre-intermediate learners' grammatical performance in English and investigated their attitudes towards grammar instruction delivered in L1. To fulfill these purposes, a homogenous group of 20 language learners was randomly divided into an experimental group (n =10), which received grammar instruction through the metacognitive intervention delivered in L1, and a control group (n =10), which received the instruction only in English without grammar instruction through the metacognitive intervention delivered in L1. The results of the independent samples t-test indicated that the experimental group did not outperform the control group in terms of all four English grammar points, namely present perfect, simple past tense, comparative and superlative adjectives, and past progressive. In addition, the findings obtained from the fivepoint Likert scale questionnaire which was distributed among the ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ــــــ ــــــــــــ
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.