This essay aims to disentangle the complex issues surrounding common ownership by institutional investors, and suggest a holistic approach that brings together the corporate with the competition law aspects of the problem. Accordingly, the analysis first sheds light on the corporate governance dimensions. Next, it outlines the theories of harms that correspond to the distinct forms and levels of shareholder activism or passivity. It then revisits the existing legal and policy antitrust framework and compares the EU versus the U.S. experience. Finally, it wraps up the discussion with some concluding remarks on the EU competition law outlook.