HOW TO ASSESS THE QUALITY OF THE TRANSLATION AND WHAT CRITERIA TO BE USED FOR EVALUATING IT, HAS ALWAYS BEEN A PROBLEMATIC ISSUE IN TRANSLATION STUDIES. WITH THE RISE OF TRANSLATION STUDIES AS A NEW SCIENCE, TRANSLATION ERROR ASSESSMENT HAS MOVED TOWARD MORE SCIENTIFIC APPROACHES, AND THE RELATED FRAMEWORKS PROPOSED FOR ERROR IDENTIFICATION AND ASSESSMENT ARE INTEGRATED MORE AND MORE. ERRORS EMERGE AS THE RESULT OF SOME FACTORS. THREE MAIN PERSPECTIVES ARE INVOLVED IN EACH TRANSLATION WHICH INCLUDES: CULTURE, SYNTAX AND SEMANTICS. THEREFORE, TRANSLATION ERRORS OCCUR AS THE RESULT OF INCOMPETENCE IN ONE OR MORE THAN ONE OF THESE CATEGORIES. GIVEN THE IMPORTANCE AND THE PRECISION REQUIRED IN THE TRANSLATION OF RELIGIOUS TEXTS, THIS RESEARCH, AIMED AT THE ANALYSIS OF THE TYPE AND FREQUENCY OF THE ERRORS OCCURRING IN THE ENGLISH TRANSLATION OF ISLAMIC TEXTS BY IRANIAN TRANSLATORS AND ANALYZE THE POSSIBLE CAUSE OF THE ERRORS. TO THIS END, 9 ISLAMIC TEXTS AND THEIR ENGLISH TRANSLATIONS WERE SELECTED. THEN, USING MORGAN'S SAMPLE SELECTION TABLE, THE ERRORS WERE CATEGORIZED BASED ON THE CLASSIFICATION OF ERROR TYPES DEVELOPED BY LIAO (2010). THE RESULTS OF THE STUDY REVEALED THAT THE REGISTER CATEGORY WAS THE MOST FREQUENT ERROR AREA.