The high competition in the business world with many competitors has forced the company to develop its business, one of them by diversification. This study aims to investigate the influence of diversification level, segment numbers, and industrial sector types on firm performance measured by the excess value. The theory underlying this research is agency theory, which describes the relationship between the company owner with the company management, The number of samples of this study are 333 companies from miscellaneous industry sector, and consumer goods sector, and basic industry and chemicals sector listed on the Indonesia Stock Exchange throughout 2017 – 2018. 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