PurposeMany emerging economy firms are under foreign owners' pressure to embrace the challenges of addressing corporate social responsibility (CSR) and consider adopting sustainability initiatives. However, it is not clear how foreign ownership plays a role to enable or inhibit these emerging economy firms from translating sustainability initiatives into improved financial performance. Utilizing neo-institutional theory, the authors argue that emerging economy firms that voluntarily report sustainability gain legitimacy in the eyes of shareholders and improve stock market performance. However, emerging economy firms may not have the resources to reconcile the internal stakeholders' various legitimacy requirements to promote sustainability practices, resulting in a negative association with accounting performance. Foreign ownership attenuates the relationship between sustainability reporting and firm performance due to the different legitimacy requirements in foreign markets.Design/methodology/approachTo test the study’s hypotheses, the authors collected and analyzed a large sample of publicly listed firms between 2010 and 2016 in Taiwan where the types of foreign ownership include foreign trust funds, foreign financial institutions and other foreign legal entities. Regression analyses were conducted to investigate whether the firms that report their sustainable practices have better financial performance, including stock market performance and accounting performance. Additionally, a three-step procedure was employed to address the endogeneity issue with a binary explanatory variable.FindingsThe positive stock market reaction to the emerging economy firms' voluntary sustainability reporting supports legitimacy gained among investors. By contrast, sustainability reporting has a negative association with accounting performance due to the difficulty of reconciling different legitimacy requirements among various stakeholders in emerging economies. Further, foreign ownership, particularly the trust fund, exhibits a negative moderating effect on the relationship between sustainability reporting in aligning corporate practices with sustainable development goals (SDGs) and the company's stock market performance.Originality/valueBy examining the less tested contingent role played by foreign ownership in the emerging economy firms' sustainability reporting, the authors provide insights into the influence exerted by different types of foreign ownership on firms' financial performances beyond previous studies that focus on family ownership, state ownership, or managerial ownership in emerging economies. The findings shed light on corporate sustainability strategy and foreign direct investment policies for an emerging economy.