This study develops an open-economy Schumpeterian growth model with endogenous takeoff to explore the effects of exports on the transition of an economy from stagnation to innovation-driven growth. We find that a higher export demand raises the level of employment, which causes a larger market size and an earlier takeoff along with a higher transitional growth rate but has no effect on long-run economic growth. These theoretical results are consistent with empirical evidence that we document using cross-country panel data in which the positive effect of exports on economic growth becomes smaller, as countries become more developed, and eventually disappears. We also calibrate the model to data in China and find that its export share increasing from 4.6% in 1978 to 36% in 2006 causes a rapid growth acceleration, but the fall in exports after 2007 causes a growth deceleration that continues until recent times.