Moderator hypotheses involving categorical variables are prevalent in organizational and psychological research. Despite their importance, current methods of identifying and interpreting these moderation effects have several limitations that may result in misleading conclusions about their implications. This issue has been particularly salient in the literature on differential prediction where recent research has suggested that these limitations have had a significant impact on past research. To help address these issues, we propose several new effect size indices that provide additional information about categorical moderation analyses. The advantages of these indices are then illustrated in two large databases of respondents by examining categorical moderation in the prediction of psychological well-being and the extent of differential prediction in a large sample of job incumbents.