The Dow Jones Sustainability Indices (DJSI), a global standard for monitoring environmental, social, and governance (ESG) investments, has included Mitsui Chemicals. Following the index's annual assessment for 2021, Mitsui, which was first introduced to the DJSI Asia Pacific in 2018, has now managed to keep its listing for a fourth consecutive year.

The DJSI, developed by S&P Dow Jones Indices LLC in the United States, assesses corporate sustainability based on economic, environmental, and social variables in order to identify the most sustainable businesses. In 2021, 153 firms – including 77 Japanese companies – were selected for the DJSI Asia Pacific, which encompasses nearly 600 important companies in the Asia–Pacific area.

Mitsui Chemicals has also been chosen for inclusion in the FTSE4Good Index Series and the MSCI ESG Leaders Indexes, both of which are global investment indices similar to the DJSI. Mitsui Chemicals has also been selected for inclusion in four more stock indices used by Japan's Government Pension Investment Fund (GPIF), the world's largest retirement fund. According to the firm, these are the FTSE Blossom Japan Index, the MSCI Japan ESG Select Leaders Index, the MSCI Japan Empowering Women Index (WIN), and the S&P/JPX Carbon Efficient Index.