ABSTRACT This study adds another perspective on corporate diversification and asset investment diversification, including related and unrelated asset investment diversification, and examines the relationship between this diversification, business diversification, and performance. Because business diversification includes related business and unrelated business diversification, we developed a hypothesis that related business acts as a mediating factor between related asset investment diversification and performance. Similarly, unrelated business plays a mediating role in the relationship between asset diversification and performance. We applied a general linear structural model (GSEM) to panel data on 470 firms listed on the Vietnamese stock exchange from 2008 to 2015. The empirical evidence demonstrates that related assets increase their performance through the mediating effects of related business. By contrast, unrelated assets show an insignificant impact on performance, and unrelated business does not play a mediating role between asset diversification and performance.