Independent auditors and managers, as key corporate oversight mechanisms, can prevent agency conflict and play a positive role in increasing company performance. The purpose of this study is to investigate the Interaction Effect of Auditor Industry Specialization and Ownership Concentration on Investment Efficiency. The statistical population of the study is all companies listed on the Tehran Stock Exchange and using the systematic elimination sampling method, 146 companies were selected as the sample of the research in a 9-year period between 2013 and 2020. The method used to collect information is a library and the relevant data for measuring variables were collected from Codal website and companies' financial statements and then Eviews software was used to test the research hypotheses. The results of testing the research hypotheses showed that there is a positive and significant relationship between auditor Industry Specialization and investment efficiency; There is a positive and significant relationship between ownership Concentration and investment efficiency, and the Auditor Industry Specialization strengthens the relationship between ownership Concentration and investment efficiency.