Despite vociferous calls for judicious use of learners' mother tongue over the past few decades, deciding on the right amount has still remained a challenge for many teachers. This article reports on the results of a survey drawing upon the views of 110 Iranian EFL teachers about eight perceived functions of L1 (Persian) in young English learners' classroom. In order to triangulate the survey results, semi-structured interviews were also conducted. The findings depicted that the teachers heavily relied on Persian in all situations except assessing the learners. Also, the main themes of the interviews suggest that teachers had better provide young learners with ample L2 input in order to help them construct desirable bilingual identities. Overall, the conclusion calls for prudent use of mother tongue with young English learners.