Intellectual Property Rights (IPR) protection is widely regarded as an important factor in technology transfer. This study empirically examines the effect of effective patent enforcement on technology transfer between US parent firms and their majority-owned overseas affiliates over the period of 1999-2005. It is found the improvement of IPR protection encourages internal technology transfer among multinationals, especially for middle-income countries. Then, in patent-intensive industries, strengthening patent enforcement level also has a significant positive impact on technology transfer within multinational firms. The conclusions reveal the impact of IPR policy on intra-firm technology transfer varies across two dimensions:host market and industry. JEL Classification:C23, F23, O34