The rise of online voicing and campaigns empowered by digital technologies and online social media is rejuvenating retail investor activism that has been mostly ignored in the traditional offline setting. This article argues that online activism that is initiated by retail investors will affect managerial attention intensity and attention priority on environmental issues, thus promoting green innovation. Using a Chinese-listed companies database with 13,795 firm-year observations over the period from 2011 to 2018, our results confirm that online environmental activism induces corporate green innovation. Online activism is more effective when the retail investor base holds larger shares in total and presents questions with a more intensely negative tone. Additionally, the above-mentioned moderating effects are stronger in digital firms. Our study offers insights into the online patterns of shareholder activism in the digital era and highlights the role of minority voicing in promoting corporate sustainable transformation.