In this chapter, the interplay between open innovation (OI) and knowledge management (KM) in small and medium-sized enterprises (SMEs) is addressed. More precisely, the three OI archetypes, which are the outside-in and inside-out processes, and coupled process, are used to show this interplay. It is shown how SMEs can benefit from applying these three archetypes and what are the preconditions for applying them in the best way.