We investigate the unintended real effects of regulator-led minority shareholder activism on corporate innovation. We use manually collected data from the China Securities Investor Services Center (CSISC), a novel regulatory investor protection institution controlled by the China Securities Regulatory Commission (CSRC) that holds 100 shares of every listed firm. We find that by exercising its shareholder rights, the CSISC substantially curtails the innovation output of targeted firms. This effect is amplified in cases involving a high level of myopic pressure and few innovation incentives. We further observe variation in the real effects of different intervention methods. Textual analysis reveals that CSISC intervention with a myopic topic and negative tone contributes to a decrease in innovation. The results of a mechanism analysis support the hypothesis that regulator-led minority shareholder activism induces managerial myopia and financial constraints, impeding corporate innovation. Furthermore, CSISC intervention not only diminishes innovation output but also undermines innovation efficiency. In summary, our findings suggest that regulator-led minority shareholder activism exacerbates managerial myopia to cater to investors and financial constraints, ultimately stifling corporate innovation.