Many firms are now implementing Open Innovation. However, measuring the value generated by Open Innovation initiatives remains a challenge. On the one hand, many initiatives deliver impact only in the medium to long term. On the other, most of the benefits are intangible and often difficult, if not impossible, to quantify. A clear understanding of the mechanisms—both internal and external—that determine when and how companies can fully capture value from Open Innovation is still lacking. So far, only preliminary approaches to measurement systems and key performance indicators have been developed, underlining the need for more robust frameworks to assess and maximize the true impact of Open Innovation.