Why does the public pay attention to some issues over others? In my dissertation, I explore the impact of non-governmental organizations (NGOs) on issue salience among the public of the Global North. Existing research shows that leading NGOs (well-recognized NGOs) have agenda-setting power, but little is known as to when and how this power is constrained. I propose two types of NGOs based on the ability to adopt a new issue: leading NGOs (able to adopt a new issue) and issue-specific NGOs (unable to alter issue foci after organizational founding). I argue that issue-specific NGOs fix a subset of public attention on their own issues through various mechanisms, thereby constraining the power of leading NGOs. I test the implications of my argument with mixed-methods, such as text analysis, regression analysis, and process-tracing.