In socially responsible investment (SRI), engagement forms one of the core strategies of institutional investors. In investigating the case of Dutch pension funds, this study answers the following questions: what networks shape engagement with investees, and what factors determine the effectiveness of engagement? The methods we used were interviews and a multiyear survey. Engagement was practised by 82% of the largest Dutch pension funds in 2016 and was implemented by asset managers and service providers. However, these actors are isolated from actors outside the financial sector. The legitimacy of the investor influences the effectiveness of engagement, whereas the number of shares is less important. The relationship between the engager and investee and the receptivity of the investee towards engagement are also of importance. Engagement can be made more effective when pension funds focus on specific themes, target companies open to engagement, and also seek collaboration with societal and policy actors.