Article dans une revue: How do immigrants promote exports? To answer this question we propose an empirical framework allowing to disentangle the role of migration networks that operate at a bilateral level from that of productivity channels (knowledge diffusion and increased workforce diversity) that operate at the aggregate level. We find evidence supporting both, at the extensive as well as at the intensive margin. The results are robust to using various IV strategies. While richer countries’ exports tend to benefit more from immigrants’ diversity (especially in sectors characterized by complex production processes), developing countries benefit from knowledge diffusion more.