Results from a large sample of Chinese A-share listed companies during the period from 2003 to 2018 show that institutional ownership can significantly prevent listed firms from opinion shopping via switching signing CPAs. That impact depends on the quality of internal and external governance environment and varies with types of institutional investors. But the impact doesn't vary with the stability and dedication of institutional investors. Although the number of institutional investors alone can significantly restrain opinion shopping, its marginal effect disappears with the inclusion of institutional ownership. The results provide positive evidence on the governance efficacy of institutional investors, and provide insights into how to foster medium and long-term investors to improve the quality of listed firms.