Our objective is to analyze whether financial knowledge influences income inequality. For this purpose, we resort to a new index of financial knowledge that differs from the existing ones in that it is both longitudinal and macroeconomic. We use this index as one of the explanatory variables of the Net Gini Index in our panel data estimations. Based on a sample of 63 countries over the period 2008–2014, our results allow us to conclude that financial knowledge is related to income inequality and that, moreover, this relationship is non-linear. Thus, increases in financial knowledge could reduce income inequality when starting from relatively low levels of such knowledge. However, at a certain threshold, the income redistributive effect of financial knowledge could disappear or even reverse. Even so, national strategies for financial education could be useful to achieve economic equity in those countries where financial knowledge levels are low. In addition, we shed light on the effect that other variables (such as institutional quality or under-education) have on income inequality.