The rising voter support for populist parties in Western Democracies in recent years has incited academic interest in populist voters and attitudes connected to the voting propensity of populist actors. In line of this research, numerous scales to measure populist attitudes among voters have been proposed. In most cases, however, the measurement of populist attitudes was tailored to specific countries and its applicability to cross-national research on populism was not assessed. This article uses a cross-national survey to assess the measurement invariance, reliability, and validity of a deductively developed inventory for populist attitudes. The findings suggest that there is a common attitudinal base to left- and right-wing populism which may be measured reliably and invariantly across nations.