Attention to sustainability reporting has attracted increasing attention in recent years. Sustainability reporting in a general definition includes disclosure of financial and non-financial information. One of the most important factors affecting companies' risk and financing costs is information asymmetry and agency costs. Therefore, the purpose of this study is to investigate the effect of corporate sustainability disclosure on the cost of equity and unsystematic risk. This research is practical in terms of purpose and analytical in nature. To collect its data, the financial statements of the Tehran Stock Exchange companies were used, and for their analysis, Eviuse software version 10 was used. The statistical sample of the research is 105 companies from the companies admitted to the Tehran Stock Exchange during the years 2015 to 2021. The findings of this research show that there is a negative and significant relationship between sustainability disclosure and cost of equity and unsystematic risk. It means that by increasing sustainability disclosure, unsystematic risk and equity cost will decrease.