This paper theoretically and empirically investigates the home-country effects of a firm's outward foreign direct investment (OFDI) activity, specifically OFDI motivated by lower labor costs in the host country. A two-country imperfect competition model is developed, and the interaction between a firm's R&D spending and its OFDI is examined. It is found that the relationship between a firm's OFDI and its domestic R&D is indeterminate because there is a complementary effect as well as a substitution effect induced by OFDI activity. Panel data on Taiwanese manufacturing firms from 1992–2005 are applied to test the validity of the theoretical results. The propensity score matching method is used to construct a comparison group without selection bias. Our empirical evidence reveals that a Taiwanese firm's OFDI is positively related to its domestic R&D spending, particularly in R&D-intensive industries.