This paper studies how the timing of NGO activism shapes its effectiveness in influencing corporate behavior. Using data on 2,500 campaigns targeting U.S. firms, we show that campaigns timed at annual general meetings (AGMs) generate large visibility gains but little contemporaneous influence, while campaigns launched before the AGM significantly increase shareholder proposal success and improve firms’ environmental and social performance. We develop a dynamic model in which NGOs trade off awareness building and credibility formation, generating a lifecycle in activism from visibility-seeking to influence-oriented engagement. Therefore, NGOs’ objectives evolve endogenously to coordinate shareholder pressure and shape corporate behavior.