This paper is based on previous studies in applying propensity score methods to study multiple treatment variables to examine the causal moderator effect. The propensity score methods will be demonstrated in a case study to examine the causal moderator effect, where the moderators are categorical and continuous variables. Moderation analysis is an important approach to examining the treatment effect heterogeneity in intervention studies. It is essential to assure that the treatment heterogeneity is solely due to the moderator. This paper proposes good propensity score applications in causal moderator analysis. The procedure of applying propensity score methods, as illustrated in a case study, will provide suggestions to researchers in conducting causal moderator analysis, such as analysis of the effects of implementation fidelity on treatment effects. (Contains 6 tables, 2 figures and 2 footnotes.)