The purpose of this research is to examine and analyze the impact of related party transaction, profitability, Leverage and size of a company on firm value with tax avoidance as an intervening variable. The telecommunication and media sector in Bursa Efek Indonesia and Bursa Malaysia is chosen as the research object. The population is all the telecommunication and media companies listed in Indonesia stock exchange (IDX) and Bursa Malaysia within 2010-2018. It consists of 6 Telecommunication Company and 19 Media Company on IDX within 2010-2018. There exist a total of 33 companies in both the telecommunication and media sector in Bursa Malaysia. The sample's determination in this study is based on the nonprobability sampling method with the purposive sampling technique, in which the sample is selected with certain considerations or specific criteria. So that the sample of Malaysia is 248 and Indonesia is 139 data. Malaysia's telecommunications sector has 18 companies, and Indonesia has five companies. Meanwhile on media sector Indonesia consist of 15 company and Malaysia 12 company. This research adopts secondary data and multiple regression analysis for the regression to substructure I and II. The hypothesis mediation analysis is used to prove the mediation influence. Malaysia and Indonesia's results on Firm value: (1) Related party transaction has a positive but not significant impact. In contrast, Indonesia has a significant positive impact (2) Profitability has a significant negative impact both in Indonesia and Malaysia (3) Leverage has positive. However, not significant impact in Malaysia and Indonesia (4) Size of the company has a negative and significant impact for both country (5) Tax Avoidance has a negative but not significant impact. In contrast, Indonesia has a positive and significant impact on firm value. Related to the impact of variable independent toward tax avoidance, based on Malaysia's result, just the size of a company has the impact but negative and significant. Meanwhile, in Indonesia, Related party transaction and Leverage were known to have a negative and significant impact, and the size of the company has positive and significant toward tax avoidance. Based on Malaysia's result, tax avoidance does not impact all the independent variables on firm value. Based on Indonesia's result, the impact of company size on firm value is mediated by tax avoidance (Z). Based on the independent t-test, the variables that have different mean values are related to party transactions and company size. Keywords: Related Party Transaction, Profitability, Leverage, Size of company, Tax avoidance, Firm value.