Rankings of countries on mean levels of self-reported Conscientiousness continue to puzzle researchers. Based on the hypothesis that cross-cultural differences in the tendency to prefer extreme response categories of ordinal rating scales over moderate categories can influence the comparability of self-reports, this study investigated possible effects of response style on the mean levels of self-reported Conscientiousness in 22 samples from 20 countries. Extreme and neutral responding were estimated based on respondents’ ratings of 30 hypothetical people described in short vignettes. In the vignette ratings, clear cross-sample differences in extreme and neutral responding emerged. These responding style differences were correlated with mean self-reported Conscientiousness scores. Correcting self-reports for extreme and neutral responding changed sample rankings of Conscientiousness, as well as the predictive validities of these rankings for external criteria. The findings suggest that the puzzling country rankings of self-reported Conscientiousness may to some extent result from differences in response styles.