This paper empirically investigates the threshold effects of openness on income inequality. Specifically, we use Hansen's (1999) threshold regression model to examine whether the openness-inequality link varies with the degree of a country's income. By applying the model to 62 countries during the period 1996-2005, we find that there indeed exists an income threshold in the openness-inequality link. Moreover, the opening of goods markets increases income inequality in low-income countries. However, in high-income ones trade openness has minor effects. By contrast, foreign direct investment is found to increase income inequality in high-income countries and has an unimportant effect in low-income ones. These findings suggest that to reduce income inequality, the governments need to consider their positions in the economic development process and adopt relevant openness strategies.