To increase their market shares and grow continuously, it is very important for small and medium-sized enterprises (SMEs) to expand their markets. Although various factors may influence an SME’s effort to cultivate a new market, this research focused on activities related to the search and utilization of external knowledge. After conducting Tobit analysis based on the dataset of 959 Korean SMEs included in the 2010 Korean Innovation Survey, we found that external knowledge search and utilization activities positively affect the market expansion of SMEs. This result has two implications: (1) SMEs should actively search for appropriate external knowledge sources with which they can expand their markets and reduce their dependence on internal R&D activities; and (2) they should implement an efficient corporate system to effectively absorb and utilize external knowledge inside the firms. Despite these contributions, this research has its shortcoming in that it utilized a cross-sectional dataset, which can be further analyzed by incorporating the dataset from previous and future periods.