The existence of shadow economies is an important, yet understudied, issue for international political economy and development. This study examines how two distinct types of international economic engagement—economic openness and participation in International Monetary Fund (IMF) programs—affect the growth of shadow (informal) sectors. We theorize that increased economic openness will reduce the size of countries’ shadow sectors. More specifically, we posit that eliminating market-distorting trade barriers will decrease the incentives for shadow sector activities such as smuggling. Additionally, we posit that increased participation in global production and supply chains is likely to lead to a positive, “climb to the top” effect on states’ regulatory and labor policies that enhance the prospective benefits associated with formal sectors. Conversely, we argue that participation in IMF structural adjustment programs can lead to great shadow sector activity as IMF-imposed structural conditions might cause significant near-term economic hardship and degrade states’ regulatory capacity. The results from a panel of 145 countries from 1971 to 2012 indicate that economic openness reduces the size of the shadow economy, while participation in IMF programs is significantly related to a larger shadow economy. These findings have important implications for understanding how the divergent forms of international economic engagement might affect shadow economies.