The working alliance is one of the most consistent predictors of outcome. Yet, little empirical knowledge exists on how therapists can use this association to maximize the outcome of cognitive behavioral therapy (CBT) for individual clients. The present study aimed to examine pre-treatment client interpersonal characteristics that determine what function the alliance should fulfill in order to maximize its effect on outcome. We did so by identifying moderators of the within- and between-clients effects on outcome. Data of 185 clients receiving CBT treatment was disaggregated to study the effects of the within- and between-clients alliance on outcome. Findings suggest that for clients who described themselves as overly cold and were described by their therapists as low on intrusiveness, state-like strengthening of alliance predicted better outcome, and that for clients not overly cold but overly exploitable, the general tendency of the client to report stronger alliance was associated with better outcome.