The central finding of system justification theory is that individuals have a psychological need to support, defend and justify their social system. While this motivation is thought to exist (to varying degrees) in all individuals, members of disadvantaged groups may have a stronger system justification motivation than members of advantaged groups. Such a disparity would be consistent with a prediction from system justification theory that we call the inequality-induced motivation hypothesis: the idea that inequality itself has a causal effect on individuals’ level of system justification motivation. This hypothesis yields the counterintuitive prediction that people disadvantaged by a system should be equally or even more likely to rate the system as fair, possibly making political responses to inequality less likely as inequality grows more extreme. Research on this hypothesis to date has been based on cross-national survey data and has provided mixed results. In this paper, we take an experimental approach and ask whether economic inequality activates the system justification motivation. In addition, we compare different ways of measuring the system justification motivation, asking whether some of the null results in survey research have been due to the availability of only imperfect measures. Across three studies with a range of different samples, experimental treatments, and outcome measures, we find no evidence that information about economic inequality increases system justification motivation.