Debates about the utility of conscientiousness as a predictor of job performance have focused primarily on mean effect size estimates, despite theoretical and empirical reasons to expect variability across situations. The present study meta-analytically demonstrates that occupation-level situational strength is one important source of this variability. Consistent with theory, predicted uncorrected conscientiousness–performance correlations ranged from r = .09 to .23 (overall performance) and r = .06 to .18 (task performance), with stronger correlations observed in weak occupations. These results highlight the need for continued inquiry into the nature of situational strength, its impact on other predictor–outcome relationships, and the implications of these issues vis-à-vis theory and practice. Copyright © 2009 John Wiley & Sons, Ltd.