The success of open innovation has been widely acknowledged in both industrial practice and academic research. However, we understand much less about the limits of open innovation. A better understanding of this downside is nevertheless very important as there are still many organizations that struggle when trying to implement an open innovation strategy. At the same time, some research has pointed to decreasing returns to openness, or more generally to the compex relationship between open innovation and (financial) performance. This is why we call for more attention to failures, risks, and costs — and even the “dark side” — in the context of open innovation. In this editorial, we will further introduce this perspective, describe the articles published in this special issue, and offer some suggestions for future research. Overall, we believe that a better understanding of the limits of openness will allow for a more balanced view, thereby further expanding the frontiers of open innovation practice and theory.