This study examines how institutional investors' active expression of dissent is evaluated in the capital market through credit ratings. Shareholder activism aims to actively intervene in corporate management activities to reduce agency problems between shareholders and managers and to enhance business performance. Such expressions of dissent by institutional investors may have a positive influence through a monitoring effect that keeps management in check; however, if the opposing agenda itself is perceived as information or a signal that shareholder interests are being undermined, or if it is interpreted as indicating problems in the firm's corporate governance, it may also have a negative impact on the market. The analysis results showed that higher levels of dissent expression by institutional investors had a negative effect on the firm's credit rating. This is interpreted as indicating a higher likelihood that institutional investors' shareholder activism is received as a negative signal suggesting problems in the firm's corporate governance, rather than being positively valued. The results of this study present negative outcomes regarding the effects of institutional investor activism, which implies that there are practical constraints on institutional investors' ability to effectively monitor and check management, and this is expected to draw attention and awareness to the role of institutional investors. Additionally, this may be interpreted as suggesting that the introduction of stewardship codes for institutional investors, which the government has been promoting, may not exclusively have positive functions. On the other hand, the results of this study can also be interpreted as the market making appropriate evaluations precisely because institutional investors faithfully performed their roles. That is, because institutional investors actively voiced concerns about the firm's problems, the market's evaluation aligned in the same direction as the institutional investors' concerns, and from this perspective, one may reconsider the role of institutional investors once more.