This paper attempts to deepen understanding of the relationship between open innovation (OI) and firm performance in small and medium-sized enterprises (SMEs). Based on survey data from 306 Korean innovative SMEs, the results of this study show that:(1) broad and intensive engagement in OI and cooperation with external partners are positively associated with firm performance;(2) technology and market-oriented OI modes (Joint R&D, user involvement and open sourcing), involving relatively low level of changes, can positively contribute to performance enhancement; and (3) innovative SMEs benefit from working with non-competing partners, such as customers, consultancy/intermediaries and public research institutes. This work has broadened the evidence available on SMEs’ OI adoption and has proposed a new way to study OI adoption and implementation.