There are numerous approaches to psychotherapy with distinct underlying theories. Yet, it is unlikely that any of these is conclusive because they broadly yield similar therapeutic effects. A different approach attempts to derive the common factors from the specific treatments and proposes that these common factors primarily promote therapeutic effects. But although generally promising, these common factors have not been integrated into a more fundamental explanatory framework that also considers the effectiveness of specific factors. Therefore, an integrative model of psychotherapeutic interventions is still missing. The aim of this paper is to help fill that gap by applying the theory of predictive processing to interventions from various psychotherapeutic approaches, including cognitive behavioural therapy, client-centred therapy, and psychoanalysis. The analysis results in the predictive processing model of psychotherapeutic interventions (3PI model for short). The new model reveals that psychotherapy comprises two main functions: to provide a safe and positive environment to which the patient can adapt, and to facilitate the process of updating a dysfunctional generative model. Further, it shows that common factors primarily promote the first function, while specific factors mainly support the second function, offering a new perspective to the debate on common and the specific factors.