Aside from the time-series macro analyses in the existing literature, this paper examines the effect of internationalization on male wage differentials from the micro data point of view, focusing on various marginal effects derived from foreign direct investment (FDI) in countries at different levels of development. Results show that FDI in OECD countries brought technology learning effects to benefit skilled labor wages, while FDI in non-OECD countries dampened unskilled labor wages due to comparative advantage principles. Consequently, FDI enlarged wage differentials between skilled and unskilled labor regardless of the investment in OECD or non-OECD countries. Furthermore, it is worthwhile to note the existence of significant effects of lagged FDI on wage differentials,