This paper contributes to the empirical literature by providing a quantitative measurement of the influence of regional trade integration on productivity. For this purpose we address the link between trade and productivity thanks to knowledge spillovers in a multi-country model. The interdependence that connects countries in an international web promotes exchanges of goods, services, people, capital and hence ideas, knowledge, innovation, and technology. Economic integration encourages thus both new ideas and their diffusion. We observe that a country's productivity depends on its own R&D efforts as well as the R&D efforts of its trading partners. These R&D spillovers can then spread across countries and sectors. Thanks to the transfer of technology allowed by bilateral trade and investment, regional trade integration has a positive impact on long-term growth.