Research summary: In this article, we address the role of R&D offshoring strategies in the sales growth of small‐ and medium‐sized enterprises (SMEs). We propose that different governance modes of R&D offshoring—insourcing versus outsourcing—may lead to growth, but that they differ in their effects. In turn, we argue that innovation mediates the relation between international R&D sourcing strategies and sales growth. Based on a large database of SME manufacturing enterprises in Spain, we find that offshore outsourcing positively affects sales growth both directly and indirectly, while offshore insourcing only affects sales growth indirectly via innovation results. The analysis reveals different contributions of each governance mode to sales growth and the mediating role of innovation in the relation between R&D offshoring and firm growth. Managerial summary: We analyze how different governance modes of international R&D sourcing—offshore insourcing and outsourcing—may contribute to growth in SMEs. Modes of offshore R&D outsourcing positively affect the growth of sales in two ways. One effect is direct, produced by improved efficiency, flexibility, enhanced resources, and access to new markets. And the other effect is indirect as offshore R&D outsourcing favors the achievement of innovations, and this in turn, positively affects firm growth. For their part, captive modes only exert an indirect effect. Offshore R&D insourcing contributes to the achievement of innovations, and thus, ultimately to firm growth in so far as these innovations enable SMEs to increase sales. Therefore, innovation results perform a mediating role in the relation between R&D offshoring and sales growth. Copyright © 2015 John Wiley & Sons, Ltd.