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This study examines the controversial debate of the exclusion of adult learners’ native language by reporting learners’ and instructors overwhelmingly positive perceptions of its use in English for Specific Purpose (ESP) classes. In this study, multiple methods such as class observations, questionnaires and interviews were used. The research was undertaken in 14 ESP classes for the students of Engineering, Sciences and Humanities at Yazd University, Iran. Extensive qualitative and statistical analysis of the questionnaires revealed that a solid majority of learners from different academic majors and instructors responded positively regarding the use of native language as a pedagogic device for teaching various aspects of the target language. Correspondingly, class observations revealed that all the instructors teaching different academic disciplines resorted to the native language as an appropriate medium for cross-lingual, cross-cultural comparisons. Nevertheless, the results from the interview phase of the study revealed that a large majority of learners and instructors were not in favor of using the first language as a facilitating technique and as a means to reduce students’ anxiety.