Objectives This study examines the effect of countries’ wealth on individuals’ willingness to pay for environmental protection. Former studies using the International Social Survey Programme (ISSP) report a positive effect, while studies using the World Values Survey (WVS) or the European Values Study (EVS) find the opposite. In this article, we explain and reconcile these opposing findings. Methods First, we analyze the three data sets (ISSP, WVS, and EVS) separately by applying multilevel analyses and replicate the different findings. Second, we take respondents’ acquiescence into account and demonstrate that wealth has a positive effect on the willingness to pay in the combined data set. Results Respondents in poorer nations in Asia and Eastern Europe have higher levels of acquiescence than respondents in richer Western nations. This difference conceals the wealth effect of studies analyzing the WVS or EVS. If acquiescence is properly taken into account, the wealth effect is confirmed. Conclusion Theory predicts that wealth and the willingness to protect the environment should be positively associated. This wealth effect is confirmed by our analyses of the ISSP, WVS, and EVS.