In spite of these important differences at different levels ofanalysis, only one study (Zilcha-Mano et al., 2016) incorporated amultilevel framework using the APIM approach to unravel thenuanced interdependence between therapist and client perceptionsof working alliance and session outcome. However, Zilcha-Manoet al. only differentiated between two levels (the within-individualand between-individual levels) but did not further decompose theeffects at the between-therapist level. In the current study, weaimed to address this critical limitation in past research by usingAPIM in a three-level multilevel modeling framework to moreclearly differentiate the effects at different levels conceptually andstatistically.