This paper studies the functional specialization of SMEs' technological competence and its moderating role in the effect of external R&D on their innovative performance. Technological competence consists of many functional dimensions such as basic research, product architecture, process construction, testing, and evaluation, which constitute a sequence of innovation tasks. The specialization of technological competence allows SMEs to utilize economies of specialization in R&D, enhance their bargaining power and appropriability conditions in the process of external R&D, and attract promising R&D partners. However, competence specialization may hamper SMEs' capabilities to coordinate and integrate diverse external R&D projects. Using a sample of SMEs in Korean manufacturing industries, we find the following results. First, competence specialization positively moderates the effect of external R&D on SMEs' innovative performance. Second, the positive moderating effect of competence specialization diminishes as the share of external R&D increases. Third, the moderating effect of competence specialization differs across industries depending on the degree of market dominance by a few large firms (i.e., market concentration) and the novelty of technologies pursued by SMEs in each industry.