The purpose of this study was to investigate the relationship between students‘ explicit knowledge in grammar and their translation ability. The importance of grammatical knowledge and its effectiveness in translation quality motivated the researcher to run this study and consider grammatical knowledge in Per- sian as the source language of Iranian students. It is clear that grammar is an area that may merit some level of explicit teaching in English translation curriculum, particularly if explicit knowledge is in the grammar of the source language. Through a Language Proficiency Test, Explicit knowledge of Persian Grammar Test, and Translation Ability Test, the explicit grammatical knowledge in Persian and the trans- lation ability of 60 translation students at Islamic Azad University were measured. The result demonstrat- ed that there was a moderately significant relationship between the students‘ grammatical knowledge and translation ability. On the other hand, the explicit knowledge of Persian grammar provides a significant impact on the quality of translation from English to Persian among Iranian undergraduate English transla- tion students. An implication of this study is that awareness assists practitioners to employ some practical and useful techniques of translation in order to consider more practical knowledge of structural differenc- es existing between languages as well as to reduce the learners‘ misunderstandings and to talk over the learners‘ needs in translation. تفاصيل المقالة