It has long been known that new firms are fundamental for economic growth. Starting new companies is one of the best ways to fight unemployment and to generate well-being. Therefore, attention is paid by the scientific community to start-ups, with particular empha-sis at how they generate, acquire and manage innovation. Initially, start-ups need to identify the resources necessary for innovation and later they will decide whether to develop them internally or acquire them externally. Being open to external sources is a crucial point for the success of new ventures; indeed, adopting Open Innovation processes allows start-ups to overcome their initial shortcomings. The goal of this research is to understand the literature status related to Open Innovation adoption by start-ups.